I wouldn't pay on the same day. Absolutely not.
But then I was a QS in the construction industry and I would make them aware my payments expectations at the outset in writing . Paying them on the day allows absolutely no guarantee of them returning if the work isn't up to scratch. Once you've worked on civil, new build, refurb and restoration jobs and had to have people back in time and time again in every area you've worked in, you know that jobs are not always done right first time.
I've more that once had a subby not returning to a job to complete their snagging list items because it wasn't worth the 5 per cent retention held in accordance with the contract. So how do you think you'll get them back to sort out issues when you've paid them same day?
I work with someone who was pressured massively by the company that did his loft conversion to pay the same day, before he'd even got home from work and viewed it. I inspected it for him and found several issues. I knew there would be, I knew their program was unrealistic and they must have rushed and bodged. They had, the floor boarding wasn't even properly supported in one area. This is a well reviewed highly rated firm btw.
Another issue was that they damaged his newly done expensive paint job in his hallway despite assurances they would use protection and fancy videos on their website showing everything being properly sheeted up. I at least managed to stop him paying until they had corrected their own work. However they pressured with phone calls and emails and he caved and paid before they rectified the paintwork.
Yep he's now paying for that himself.
A sustainable business should be able to raise enough credit to deal with a reasonable payment term. I wouldn't employ someone in such financial peril that they had to have cash the same day. Doesn't smack of a stable professional.
Paying in cash? Absolutely not. And why would you? Electronic transfer leaves a proper paper trail. It also helps stops tax evasion and huge amount of that goes on in construction. I've never not paid the VAT on a job by paying in cash and I'm assuming no one else on Mumsnet has given how strongly everyone felt about Rishi Sunaks wife paying more tax on a past thread.
When I had my house remodelled, you can bet my payments were done properly. Interim payments throughout, the full value on completion but only after I'd had time to do a full snagging list and a retention of 5 per cent held. I've never released it as they've never addressed certain issues. I'm about to use some of that money to get the door sorted that's never been right.
Make sure you're fully happy with the work OP. Inspect it as well as you are able to. Take photos of what was done if you don't know what you're looking at. If you think there are any issues don't release the full amount just a percentage. Don't put up with being hassled. Tell them you'll pay them on the next working day. It no wonder there are so many cowboy builders about in England and industry lacks credibility. All the advice on this thread to rush into being someone's cash cow is so far from how professionals in the industry on projects act, it's no wonder people get screwed over so easily.