DS wants to repeat Year 13

And stop his gym membership, if he wants it, he pays for it.

The sixth form should have kicked him out in year 12. He is taking the place and funding of a child who would probably apply himself.

I think your son wants to repeat year 13 so he can keep fucking around on his phone and do no work, again. Right now I would be taking his phone, I wouldn't be paying for anything for him because his behaviour doesn't warrant it.

He isn't committed to working for his BTEC otherwise he would be showing you how much he is working. He is just giving it lip service.

My DS (just finishing year 12) has just decided A levels are not for him. He really doesn't enjoy them and has decided to leave after the mocks and has enrolled in a different college to do a level 3 BTEC in engineering instead in September. He will still be able to get into university with this if he wants to in the future.
What's the point in repeating year 13? If he hasn't bothered up until now how will he discipline himself next year?
From experience DS's school only ever pushed them all down the academic route.. very very focused on A Levels and university and there was little to no talk about what vocational courses were available elsewhere as an alternative. Maybe your DS finds the academic work of A levels just isn't for him? I left A levels after a year, did a GNVQ instead and then went to university to study nursing, best decision I ever made.
Maybe your DS would do well to look at what his other options are now outside A levels? No point wasting another year if he really hates it. The funding is an issue but shouldn't be a barrier if there's something eh really feels passionately he'd like to do instead.

I think he is wanting another year because it's a comfort zone
This ^^. He knows he doesn't have to put any effort in for another year, unlike if he had to get a job.

I suspect, being bright he has found everything too easy up to now and rather than be up towards the top of the class he could maintain middle of the road without putting any effort in and that becomes a habit.

I was like that, sailed through 'o' levels with good grades and couldn't grasp what was needed at 'a' level. Having to work was something I had never done in order to stay well up towards the top of the class in most subjects.
I think he is wanting another year because it's a comfort zone, he knows what's expected - and I suspect, how to play the system.

I would suggest he gets out into some sort of practical training that suits him. If he's interested in Kart Racing, then why not a mechanics course. That would also give him an opportunity to learn more about driving and possibly an 'in' to a cheap car, if he can work on it himself or get mates rates at the garage he works at.

I don’t want to make a dig at you OP but as parents you should have turned the wi-fi off and not paid his phone contract- in year 12 as soon as he started pissing about.

If he repeats Year 13, what are the chances he’ll get good results after crap year 12 results? It shows he doesn’t really know the work. Really he should have repeated at the beginning of year 13. I did, I changed from A Levels to B-Tec, as my predicted A Levels we’re only an A, B and C. Best thing I done.
You say other students have repeated, but they may also have valid excuses that people don’t know about, not just ‘can’t be arsed attitudes’. He may be best off getting an apprenticeship and working his way up, and saving for a long time to get himself in the road, without being rewarded for it by his parents.

People saying 'take away his phone and tell him to study' is all very well but does he actually know 'how' to study? That can be many teens problem. They are interested in what they are learning etc but the knowing how to study alone, write essays and all that they just can't 'do' and the whole thing becomes overwhelming and they shut down.

It's not really down to the school to fix this though. If he doesn't have the motivation it's not going to appear overnight.

I would stop paying for the phone tbh, and suggest he gets a part-time job to pay for it himself. You haven't said what you've done at home about him not working for his exams, what were the consequences of that?

You tell him right now that you're taking away his phone so that he can get his head down and study like he's never studied before - you keep his phone until the exam is over and if, and only if, he's made a huge effort for it you'll speak to the school about him redoing yr 13. If he can't be bothered then you'd be wasting your time and so would the teachers. But you keep the phone anyway until the exam is over. You're the parent aren't you? Put your foot down.

My brother did the dead end job route, figured out what he wanted to do with his life after a couple of years, went to uni to do a course that wouldn’t have even crossed his mind at 18 and is now in a top job. It can help.

Teenage boys can be very inconsequential. They don’t always see the longer picture and need for effort in the here and now. Some (like ours) are dragged screaming and kicking - or at least shoulder shrugging- towards academic achievement in two years. Others see the light at the end of the tunnel and need that third year.

As a parent I think we have an absolute responsibility to support or push or cajole them into the best possible academic results. I do not believe a couple of years stacking shelves with Bert in Homebase is the answer; they get stuck in dead end jobs.

Try and get him back into school until he’s ready to face the adult world (there’s no great rush) and let him do it from a position of success. Set very clear rules about school work and behaviours though.

if he was really regretful he'd be pulling his finger out for his BTEC ICT exam. If he is intelligent then he should be able to get a good grade on that with a bit of work.

he won't change by returning to the same school for another year.

He's going to continue wasting everyone's time, he really needs to get a job.

What does he say he wants to do job wise?

The problem is, 6th form funding is available for 3 years, not 4.
So by allowing him to continue to y13 the school has actually done him a disservice in some ways. If they had kicked him out after y12 he'd have got his shock, and could have restarted elsewhere, possibly on a different course. Now he wants to redo the whole thing, and there isn't funding, or any evidence he'd act differently.

I suggest you/he look into apprenticeships.

No one took the warning that was the AS results.
He didn’t pull his finger out, you didn’t take his phone off him / turn off the WiFi at 10pm or set times.

I would have had mine under a regime if he had pushed about like that in Yr12. And spoken then about repeating Yr 12.

He sounds addicted to his phone. Young people need support to help them discipline themselves.

If he is allowed to try again (and how will he catch up on the Yr 12 stuff? The A levels are linear now and include the whole course in the exam) it will have to be a whole family resolve.

Morning user20. I didn't want you to think I had abandoned the conversation - I just went to sleep.
It sounds hard. Would he sit down for a casual conversation of "what do you do on that phone all day"? You never know - there may be something there you didn't know he was interested in. He must enjoy and be interested in something. If not now but a few years back. A lot of teen interests have to get pushed aside during the gcse years.
Schools tend to focus on the get good gcse grades so you can do a levels - get good a levels so you can go to uni - then go to uni - but then what? Often all those years of study is so focused the actual end goal is forgotten. What subjects did he choose for a levels and why? Does he know what those subjects could lead to? Does he think of the ICT subject as a bit of a 'filler' subject not really knowing where that qualification will lead?
Sorry this is a bit rambling for this time of the morning.
Ask him to imagine what he would like his life to be like in 5 years time. Inside of him there will be a goal - he may not just know it. He needs to find it.

The minimum wage job for a couple of years will only work if the OP is then prepared to not charge rent etc and fund any college courses if he decides to go back to education. Will you be prepared to do that when your son is 20 or 21 years old?
What is he actually doing on his phone? Watching youtube vids? Chatting on forums? Reading random Wikipedia articles? What are his current interests. An interest can lead to a job but often teens haven't always made the connections or know how to get there. What does he enjoy OP? Or what did he enjoy at age 13/14?

Has he said why he wants to return, if he isn't working for his exam?

I’m a teacher, I know of one child it went well for. He’d picked the wrong a levels so resat year 12 with 3 new subjects. Two boys resat year 11 and will do worse than they did originally, what a waste of everyone’s time.