I just posted on this recently, glad to see more cheese people in London! We are actually pretty darn lucky. You can get pasteurised, non-homogenised milk at most major grocery stores, just check out the labels carefully. I used to use Calon Wen a lot (buy from Ocado). Waitrose has their own brand of this kind of milk (just read labels carefully regarding homog.--some that you might think are not actually are!!). There is also one at Sainsbury's and even Tesco. The going rate is about £1/litre. We don't have the same problems as the USA with ultra high temp pasteurisation being a norm.
Jersey cows have very high fat content, it is actually too high for the cheese I mainly make!!! So, just something to keep in mind as you are looking at recipes.
Raw milk is becoming more available and most farmers markets have it. Hook & Sons is the £3 one. The rest are usually around £1.50.
Hope this helps!