I think this is key.
Your child is unlikely to have the same experience at former FE college in a smallish town/city which now also offers degrees alongside other courses as they will in a large highly ranked university. Your child who wants to be a lawyer but will only get BCC in their A levels is not going to get a job as a lawyer just because the university of Smallville accepted them onto a law degree (they literally just want the cash). Your child will not have the same experience at a large city university as they will at a campus university (by which I mean fully self contained on a separate site rather than a cluster of buildings in the same part of a busy city). Your child will not have the same student experience at a central London university as they will in a smaller place. Likewise your child who loves clubbing and wants to be going to different clubs every night and mixing with non students is unlikely to be happy studying in Falmouth.
It's really important to think about the life they will have as well as the rankings of the university (which is often heavily influenced anyway by research factors which are largely irrelevant to undergraduate study anyway). This is partly because once they are established in their first job (which is increasingly likely to be something at a slightly lower level than they had been expecting due to the dire state of the graduate job market), nobody actually really cares about where they went to Uni, they care predominantly about their last job and their working experience. So yes your school will be pushing LSE and LSE is of course very highly ranked and well regarded but LSE also has a very, very high proportion of overseas students who typically don't mix outside of their own group, its central London and so you are not in an environment purely made up of students and its central London so you are likely to be living some way away - probably with students from different universities in a private accommodation block. All of those factors will have a significant impact on how easy it is to meet friends. That is going to be completely different to say Bath or Lancaster which are also top ten universities in the rankings but are in small cities which are heavily dominated by students and are self contained on green campuses where everywhere you turn you are next to another student and you are spoon fed opportunities for socialising. Lancaster for example literally has six different bars just on campus itself plus an SU run student only nightclub in the city.
Accommodation is also crucial. Collegiate universities like Oxford, Cambridge, Durham, Lancaster and York have far more of a boarding school feeling and are very community focused since they effectively split the kids into groups and each will have their own common room, sports and social teams, balls and parties, bars etc. There is inter college rivalry which adds to that "extended sixth form" /community loyalty feeling. It's a nurturing environment and it's easy to get to know people in your college due to all of the events laid on. Some kids won't want that at all and will want to feel like they're living completely separately to where they study and will prefer private accommodation and arranging their own social activities away from other students.
You really need to research carefully and think about the type of lifestyle your child wants to be living. Then you need to set their expectations. It's really pure luck who they end up living with. They can't rely on liking their flat mates.
Personally I steered my DC towards campus based universities since IMO it's the best of both worlds. If you don't hit it off with your flat mates its far easier to meet other friends and you can live off campus in years 2/3/4 if campus living is not your ideal situation.