I would not get too hung up about "levels". There seems to be a West London belief in a hierarchy which has SPGS at the top and then Putney/G&L followed by LU/WHS/NHEHS and then FH, with the various Queens bringing up the rear.
In reality all these schools are fishing in the same pool and each will have their own culture, USP and selection criteria. LU is an odd one. Half the places for girls, quite a large contingent coming through their own prep, and huge numbers applying. It is perfectly possible to be rejected by LU yet gain a place at Westminster (for boys) or SPGS. It happens. Or be accepted by LU and not gain a place at Putney or G&L.
G&L and LU appear to be very different schools. Broad generalisations, and each school will be looking for a mix, but the latter might suit a feisty co-ed, good at drama, art, or sport and perhaps with an aptitude for maths. (Just a guess, but I understand the top maths sets tend to be boy dominated so I assume they welcome girls who can help re-balance.) I assume G&L will be interested in taking a proportion who are all-rounders who might go on to IB, and also girls who with thrive in a nurturing all-girl environment.
It sounds as if you were aiming at the right schools. You only need one place - and a back up plan. Does the prep go up to 13+? If not, and after you have the results, ring round places like Thomas' Batters, Fulham Prep or Newton. Places come up at 13+ and occassional places before then, and with preparations for CE, Yr 7 in a prep school moves at a fast pace.
I hope that helped. I took about two years to get over the 11+ nightmare. Remember you only need one place.