I'm yet to see them yet, however the first port of call should be:
20A Brook Street
Whilst you're there check out the Paul smith sale shop on Avery row. Loads of bargains to grab
other shops are:
41 Wellington Street
16 Burlington Arcade
While you're in the arcade, check out NPeal If you like cashmere, also Edward Green shoes are sold here.
Caron & Lanvin - Harrods @Knightsbridge