Lk Bennett has 40% off (sale started today). Buy some good staples, they make amazing jackets, very versatile. These are suit jackets but made of soft wool.
Then, look at saks, neiman Marcus (us stores), lots of sales all the time. Note: you need to pay custom duties on those.
Don't buy cheap stuff that you need to replace next year, buy classic clothes that are well made and last forever.
I have 15 year old suits that look new (grey, black etc).
Also, whatever you do, never ever buy polyester stuff. Cotton, silk and wool. And use dry cleaning. Groupon often does dry cleaning offers in London and other cities (£15 for £50 worth of dry cleaning etc).
I wish I could come and help you buy stuff, I actually do it for a lot of people (free of course).