a haze of packing

Packing is probably the hardest thing about going to London on vacation. The dilemma is this; how much and what do I pack for freezing cold England and how much room should I leave for shopping?

I mean, obviously there will be shopping, unless it's one of those times when the time limit of a week is too much pressure and I dont find anything I want to buy (this is worst case scenario, but I guess my bank balance would be happier).

Anyway, on a cold and rainy Monday night in Cyprus, I am trying to work out how to get an adequate amount of this.....

...........into my suitcase. HELP!