What are the benefits to being on the SEN register at school?

[icanneverremember]

Sorry, me again!

My son had some issues but as yet undiagnosed. As far as the school are concerned there are no problems. His behaviour is good although he can sometimes be slightly anxious. His school work is fine and he's not struggling.
He has a problem with toileting though. He will not go without being told and frequently comes home smelling of urine as if he has leaked slightly. I know that holding his bladder chronically for long periods is bad for him and he is on regular medication for constipation which causes night time wetting. I have asked the school to ensure that he goes for a wee at lunchtime. They sometimes do it but sometimes don't bother. I've had to remind them three times to carry this out. Today there was a supply teacher who obviously hadn't been told of this arrangement.
In my opinion the school just aren't taking this seriously, not least because he has no diagnosis.
Would I achieve anything by insisting he goes on the SEN register or is that reserved for children who need extra help with their education specifically?

What is a register going to do?

If you had any other problem in life faulty computer, sore arm, blocked drains, would you be happy for the solution to be being put on a register?

Sorry, that was meant to be an exploratory question, not a critical one.

Many parents are told that their child is on the SEN register as if somehow that register is going to climb out of its filing cabinet and come and teach them how to spell.

That is exactly my question. I'm wondering being on the register would make his needs official and mean that the school is obliged to do certain things for him rather than "doing me a favour" which is how I feel it is viewed.
I also wonder whether being on such a register would mean there is information on it which will follow him through school thus negating the need for me to have meetings with every single teacher he has in the future.
Another example is that he has (mild) mobility issues. Despite this I found that his pigeon hole had been located in a position whereby he had to access it by standing on a stool. As far as I'm concerned it should go without saying that he shouldn't have to do this.
Will being on the SEN register ensure any of this? Is there something that can be done instead if not?

Just for clarity - I have no issue with having regular meetings with teachers but it's not feasible for me to necessarily capture every teacher he will come into contact with. I'm wondering if there's another way of ensuring his needs are identified by every teacher by way of effective communication.