If he was keen to study in London there's also UCL, which I don't think anyone has mentioned. As a University within London it's right up there with Imperial and LSE but unlike them covers the whole academic range: science, engineering, maths, humanities, medicine, the lot - and slap bang in the middle of Bloomsbury/ Fitzrovia. I know the physics dept is top-notch. I have no direct knowledge about the engineering but I'm pretty sure that is too. And what is more (the real clincher) they have the preserved and stuffed body of Jeremy Bentham on display in a glass case in the foyer. What more could anyone want?
I did physics at University - many many moons ago - so I am biased, but I do think it's a great choice for someone who wants to follow a career in science/ technology but is presently a bit vague about precisely what. And especially if you did a course where you started of with a broader range of scientific disciplines. The prime example here would be Natural Sciences at Cambridge. Much of a physics degree would be directly relevant to engineering and I would have thought that there shouldn't be a major problem in doing physics as a first degree followed by an engineering masters.
With engineering in many cases you have to make decisions very early one - e.g. between different machanical, aeronautical, electrical, chemical etc. Absolutely fine of course if you know what direction you want to go in.
I think it's very important too to go and have a look at various places before applying, whether on official open days or other times. Some people would be attracted by a college structure (e.g. Oxford, Cambridge, Durham), others by a self-contained campus (East Anglia, Sussex) or sizeable town/ city. I think whether you generally like the "feel" of a place is more important than whether its 2 or 3 percentage points higher lower in the league tables.
Our son, by the way, is doing Electrical and Electronic Engineering at Sheffield and really likes it. A highly regarded department in a big - but not too big - city with a proud engineering history. First year in a really nice student village.