This afternoon, I tested the new Imperial College Sport Center - Ethos. I went for a swim and that was actually pretty nice. The 25m & 5-lanes pool is relatively bright and the water very clear. No rubbish music is played and the UV disinfection system doesn't leave you with a too strong chlorine smell (that were the arguments to convice M.). It's globally modern, with a huge mirror in the changing room, individual shower temperature selectors and digital lockers. I've not tested the spa, neither the sauna and the steam room yet.
As I need to do some negative comments too, I'll just point out two things that were missing: kickboards and pull buoys (*) but also girls ;) .
I think that's the best pool I've ever been, and therefore the best free pool too :) . We'll see how all this nice stuff resists to intensive use though.

Ultra new.

(*) Up to now, when Mommas was talking about that, I thought they were "pool boy", which doesn't make much sense, does it ? :)