down to earth, warm, bit of banter
True, but compared to 20 years ago the shop was much deteriorated and on my last two trips, special effort made, no real, even slightly unusual ,corydoras species available. I used to make a visit fairly often when I lived in south London in the past and always bought corydoras. The shop was not in a good condition when I was there last year.
On the bright side, since you are in London, I visited a small but impressive shop Finsbury Park last week and bought fish. Dead easy by tube. Fish Planet, no banter, quite serious knowledgeable young staff, but super healthy fish and quite a few less usual fish and super healthy plants for sale.
If you are willing to catch a train and use a bus from central London, if corydoras are your thing, Abacus Aquatics, Sidcup is small but very good, no real banter but very friendly and good plants and nearly always live food - I by the way don't really buy the latter, happy to use daphnia I've bred and bloodworms from my water butt, but each to their own.
I can also recommend, though not quite yet fully as it is under new management, Birchwood Aquatics Swanley and, perhaps worth a visit, not so great when I was there in November, but fairly good last Spring, Aquatic Design Centre SW12, previously a really impressive shop for serious planted tank folks. For live food and staple fish, Castle Aquatics in Eltham is pretty good, though not the sort of shop you would make a real special effort to visit.