I've been here 12 years, and seen snow about 5 times. I live in the South West, and it tends to stay fairly mild during the winter - temperatures rarely get below freezing during the day, although I have been scraping ice off my car windows the past few mornings.
They do get more snow up North and in Scotland, but you won't get as much anywhere here as you will in PA. When it does snow, it is pretty special and people go a bit crazy.
If you love cold, crisp, sunny winter days (which I do) you won't get very many here - winter seems to be primarily wet and dark - but when the days are nice it really is beautiful.
Summers are nice - it rarely gets too hot (although we did have some hot weather this past summer). If you like extremes of temperature, you have to make sure you vacation away from the UK!