I am looking for advice for what type of clothing to pack for a trip to England over June and July.
You might want to Google for average highs/lows, etc. It could be sunny 80's or rainy 60's (it's not usually muggy, though). In a word: Layering. I would bring a light waterproof shell (like the kind that folds up into it's own pocket) with a hood, a sweater, a blouse or two, some t-shirts/polos, and a tank top or two (great for layering under the blouses). For pants/skirts/shoes, it depends on what you'll be doing and where you'll be going. Enjoy! I won't be there for another year. :-(
I agree with DW; choice is key. I have been there in June, July, August and September and been mostly comfortable or warm (Portland weather in spring/fall). I think the lowest temp I dealt with in evenings was about 50 and the warmest was in the 80s, so that is what I plan for.
We go to the UK every summer. I take 2 pair of cotton blend pants (black or khaki) and wear 1 pair. I pack 2 or 3 T-shirts, 1 "big shirt" that I can use as a blazer or for cooler mornings, and maybe 1 other top. Add a scarf, and a lightweight,unlined windbreaker with a hood,plus socks and underwear. My bag (Rick's convertible- 20+ years old and it looks new) weighs less than 13 lb.
The average temperature in June and July runs around 69-72. They do get some warmer days at times, but I wouldn't count on it. Take a few short sleeves, but do take long sleeves, a light weight sweater and/or jacket. Have a great trip.