I agree with many others that Warwick is well rated for maths and should surely be top of his list, with his amazing PGs. Apparently there is a lot more accommodation choice than there was so that’s not such an issue. And it’s a lovely campus as I am sure you are aware.
Short story – I was an academic star at my (selective) secondary school and only when I got to uni did I realise what it meant to be challenged by the work and amazed at others’ ability and knowledge on a daily basis. And in fact uni is often the only time in your life, or at least the main time, you can really have such an experience (unless your working environments are very different from what mine have been!).
It was salutary for me – and you do need to be resilient – but having spent the summer before my first year working in a factory to earn money, I was staggered to go to Bristol to study German and discover that many of my peers had spent two months working in Germany, and were so much more fluent than I was. It was tough but it was a good thing for me to experience.
The fact that the Leeds offer is lower and doesn’t expect FM rings massive alarm bells for me on your DS’s behalf. Unless you know he is particularly fragile (for yes, the approach above would not have worked for, for example, my DD) he should go, other things being broadly equal, to the place that demands the most of him, in terms of A levels and in terms of the course. It will stand him in good stead.
BTW yy to offer holder days – DD’s offer-holder day for her final firm choice was what really encouraged her to put it first – the staff were so inspiring and she came out so enthused. (It was Warwick as it goes but she didn’t end up there!)