I was intending to visit a few old vintage haunts on my next visit, in a month or so but my initial research shows me a lot of them have closed, or moved. I genuinely long for the days when you could stroll into Kensington Market and buy 501's for peanuts. Blackout II (Endell St) was always worth a look for ladies-wear, less so for me, although American Classics would have been a semi-regular haunt - at one point the only place to buy LVC and other interesting stuff coming in from Japan. Interstate (opposite ish) too had some interesting stuff, being one of the first places I noticed Edwin Jeans and some of the more unusual Barbour offerings. I bought an English-Made International there in the late 2000's which I still have, although it sees little use.

Rokit vintage around the corner on Shelton St was one of those places I'd probably poke my nose into every third visit, if I'm not much mistaken, it's in the building next door to where the once infamous and long gone Duffer Of St George had their shop. Covent Garden was once host to a number of smaller independent vintage clothing shoes - there was another on Earlham Street I seem to recall that had some interesting military stuff - it was in an old hardware store. This is well after the hey-day of the vintage clothing store so many of you speak about in revered tones and which I've forgotten the name of.

I occasionally look at the beyond retro website and would poke my nose into their Soho store often enough when I worked around the corner (2008-9ish). They had quite a high turn over of incredibly attractive Swedish sales girls which made the visit more appealing.

More of a trip down memory lane for me than any use AFS, sorry.

I still miss Celia and Frank in Nottingham.  Their shop was amazing - and amazingly eccentric.  You could be trying on a jacket or a pair of shoes in one corner of the fitting room while some chick was being fitted for a corset in the other.  They did party hire - a major part of their income.  Celia really had an eye.  I once had a compliment from a lady in her scanties on my seersucker jacket.  It was straight out of the 50s, like an old department store.  Frank used to stand at the ironing board. 
'Backlash' was also good.  I remember buying a lovely Lora Piana jacket from there around 2008 for about £25.

Thanks, Woof. 
An Unseen Scene once mentioned somewhere that was crammed with funky wide lapel disco plaid horrors at around £80 a throw. 
Charity shops in this neck of the woods often want £25-£30 for Daks and M&S.  Whether they get it or not is a different matter of course.

Walking away = self-discipline.

There is Hornets in a nice part of Kensington. That is more ‘gentleman’ than Ivy.

There used to a place in Fulham Broadway the proprietor used to wear baggy corduroys with braces. Closed now as he was convicted of either tax or VAT fraud/non payment. ‘Gentleman’ again though - the tweedy cyclist crowd.
https://www.mylondon.news/news/west-london-news/owners-upmarket-fulham-tailors-jailed-13722228

Used to see him on the way up to Craven Cottage.

It sounds - thus far - as if London is something of an 'Ivy League Wilderness' as far as the secondhand market is concerned (although TRS has not commented on 'Beyond Retro', the source of his Cricketeer two-button). 
'Wild' in Nottingham was one of the better locations (and still is) for 'generic Americana', with odds and ends of 'Ivy League' popping up every now and then.  The pea coat I bought from there around fifteen years ago is still giving good service, although no longer to me. 
I wonder if anyone on here browses the 'One-Off' items at Chiltern Street.