When I first read your post I was going to say to cut him some slack, because my husband owns a building company, so I know from what he tells me that all supplies are delayed at the moment
I think if there were problems getting materials, he'd have mentioned it, surely? But having said that, all the builders I know are mad busy at the moment. My BIL has his own building business, and he's not even going to look at jobs if the customer wants anything started before July, because he's booked solid for the next 3 months. When you're booking jobs back to back that long in advance, it only takes a couple of things to go wrong to put you really behind schedule.
I've only had a tradesman let me down once. He came highly recommended by local people on Next Door. He quoted a very competitive price, we gave him the go-ahead, agreed a start date and and I gave him money up front for materials by bank transfer. He turned up promptly on the Friday with all the materials, ripped down all my guttering, took all the old stuff to the tip and finished for the day. He never came back again and didn't answer calls or texts, even when I rang from a different phone.
It transpired that he had a cocaine and alcohol habit and was given to going on benders. He'd only had the money for the materials and approx £140 which he said would mostly be the cost for disposing of the old guttering etc, and I had the materials. I had to pay another builder £50 to do a temp fix on the flat roof of my bay window, as the rain was pouring straight off the roof and pissing through.
It all came out later that he'd priced the job based on doing it from ladders, then got started and realised it needed scaffolding. The cost of the scaffolding would have meant he was doing the work a quite a loss.
The guys who eventually sorted it were brilliant, but their quote was nearly £1k higher. However, they said they could fix the leaky roof as well for £250 extra while they had the scaffolding up. We'd been quoted £1.5k for the roof repair, so ended up quids in overall.
I hope it gets sorted, OP. I've learned never to hand over money without a registered address for the business now.