Pineal Eye is definitely not closing down. It's got some new stock in, I just went two days ago. These are a only a few of my London boutique reccomendations (I tried not to name too many obvious ones....coz I really want ppl to check out these hidden gems!
Souvenir on Brewer Street and Lexington Street - Stocks Westwood, Cacharel, Ashish, PPQ, Jessica Ogden, Hussein Chalayan and Martine Sitbon...and the shops are really lovely to shop in.
http://www.souvenirboutique.co.uk/
The World According To....... on 4 Brewer Street - Tiny basement store that stocks Silas and is the only Eley Kishimoto Ellesse stockist in London, I think. The guy that owns the place is also fabulous.
Start on Rivington Street (Hoxton) - A mini cool department store spread over two stores - Lots of Rick Owens, Helmut Lang and Miu Miu. There's a personal tailoring service in menswear too! Nearby is the Hoxton Boutique which has become a bit of a cliche shop to visit but still stocks some great things.
http://www.start-london.com
http://www.hoxtonboutique.co.uk/
No-One on Kingsland Road (Hoxton) - Nice cafe/shop. Selection of vintage shoes, lots of nifty gifts and clothes by PPQ and other upcoing British designers.
http://www.no-one.co.uk/
Diverse on Upper Street (Islington) - Great North London boutique. Two floors of Chloe, Missoni, Marc Jacobs and other more conventional labels. Lovely layout and wicked storefront.
http://www.diverseclothing.com/
b-Store on Conduit Street (Mayfair)
Fantastic place for Bernhard Willhelm, Karen Walker and Peter Jense for both men and women. The Buddhahood shoes are also really cool, really unusual shapes and perfect for matching with any of the advant garde labels that this store stocks.
http://www.buddhahood.co.uk/