Katherine - to be honest, I have DC at both LU and G&L and there are pros and cons to both.
At LU, 50% of entry at 11 plus is from state schools. I’m not sure if the stats got G&L, but it won’t be far off. So I think, staying where you are won’t be a disadvantage, as such, but so think a lot of state school applicants do have tutors (more for exam technique and making sure all the curriculum is covered inc more extended maths questions).
This is just my experience of course, but LU is a tougher environment in Years 7/8/9 because of the co-ed and also they tend to take quite articulate types who aren’t afraid to push themselves forward (if I can put it that way)
However, they do calm down and by GCSE / A-level they really thrive in the co-ed, diverse environment. There is a campus feel. Teaching and the curriculum are excellent.
G&L seems calmer because of the all girls vibe. They don’t play up to the boys, in other words. It’s very unpretentious and they can be themselves. DD is still in the lower years, but we’re absolutely living the school so far though and she’s settled in much quicker than my elder one did at LU,
Despite all the hullabaloo about getting in, neither of these schools feels pressured at all. Only at GCSE do they feel the pressure, but I’m sure that’s the case in every school.
I’m sure RPP will do a great prep job for either as they’re so nearby.