Prices definitely have gone up in London from earlier this year but there is of course the VAT back. However, the dollar also is slightly weaker than a couple months ago so I didn't find there to be any huge financial advantages to purchasing there this last trip. My impression from last week was that pickings were slim for Fall Act I clothing at both the stand-alone boutiques and also the department store offerings (the advantage at Harrods and Selfridges is that you can add up all purchases from any department to get a higher VAT % back). But they all were waiting for Act II in mid September. In the past I've found the best sale selection to be at the main flagship store on Bond Street.

Especially cashmere sweaters and tops. Hope you have a successful trip!