I have to disagree about leaving behind summer clothing. Unless you are going to be living in the far northern reaches of the Scottish Highlands OF COURSE you will have occasion to wear summer clothing"!!!!
I lived in Austin Texas while in the States, and it's HOT there for six months of the years. near 100 for much of the summer. Not only did I bring to the UK ALL my Austin summer clothing -- tank tops, all sleeveless tops and dresses, light clothing, flimsy clothing, sandals, strappy shoes ans yes, heels -- not only did I bring them but I found the need to wear them too, coming here in July. Those summer clothes saw me through the London July and August and even now I'm still using a tank top under a light cardigan on the balmier, milder days.
It just really irks me when people paint this picture of "oh FORGET your summer clothes, leave them behind you'll never need them in the UK!!"
That is just not the case. You won't get 100 Fahrenheit but you won't be wearing fur coats all summer either.......