Soul Jazz is the label, Sounds of The Universe the shop. There and Phonica are the best two left in Soho. Not sure if either fit your brief for feedback etc.too closely though.
Berwick Street is a disappointment really, Sister Ray is still there but a pale shadow of it’s former self.
Daddy Cool moved from there to Wood St in Walthamstow years back. I think he’s retired now. Vinyl Vanguard and Mike’s are still going in the indoor market there.
Never taken to Rough Trade East, never as good imo as West or the old Covent Garden store. Whenever I have been there, I’ve usually come out with a book or something other than actual music.
Flasback are not bad, Essex Rd usually the one I go to (occasionally)
Out on The Floor are still going in Camden but there is no other reason to go there really, for record shops anyway.
Crypt of The Wizard on Hackney Road might cross over into your tastes.
Cosmos in Dalston is my current fave, but that’s jazz and er, cosmic rather than drone et al. They have some psych though.
I used to love visiting Terrapin Trucking co. In Crouch End…long gone but Zi see they have moved to Barnet and are based in Slims Record Shop.
Kristina Records in Stoke Newington I have yet to try but might be good.
Cafe Oto has some records and cds on the weirder side of things.
Their south-of-the -river equivalent, Rye Wax, in Peckam is similar. I liked it there when I visited.