HI<BR>I don't mean to be sarcastic, but best time for what?<BR>Obviously summer has the better odds for better weather, but sunshine isn't guaranteed, and the crowds are much greater. Winter (Jan-March) is much less expensive, but you have to dress for and cope with cold and rain.<BR>In general, I love traveling in late Sept early October, but that means gardens aren't at their best.<BR>It just depends on what your priorities are.
You didn't mention where in England, but if you are referring to London, the temperatures there stay relatively mild year round (at least if you are used to extreme temps like here in Nebraska). <BR><BR>I enjoy going to London in the winter, because compared to the weather back home 40-50 degrees and rainy feels like heaven. The underground train system tends to keep the city from getting very cold.
I go every year in June, and I just love it. It is usually around the upper 60's. I have had the best luck with weather..just overcast, little rain. Yes, the crowds are the worst during that time, but it is the only time of the year I can go. I like the weather bc it is a nice change for me in June. I live in Georgia and it is around 100 degrees for me in June! Yuck! So, the 68 degree, overcast weather is a breath of fresh air for me!! 

I'd go for the last two weeks in May if I were you. The weather can be delightful at that time of year although of course you'll need to dress in layers. The gardens and parks will be looking beautiful and the main tourist season will not have started. The time NOT to come is July and August.
Thanks for all the info. I live in Phoenix so rainy weather will be quite a change. We haven't got far enough in planning to decide everywhere we want to go in England, but of course, London will be a start. What's weather in Spring like? Lots of rain?
Hi Angie- It rains, rains, rains all year round, but from the weather charts I've seen (you know the ones, with average temps, rainfall, etc.) I do think you will have a better chance of sunny days in May. That being said, it is going to be more expensive for hotels, etc. because its considered the busy season from May-September. I am going back this coming February. I live in Michigan, so it will be warmer in London, but not by much. The rain and all the humidity is the hardest thing to deal with- I always have bad hair the entire time we are there
The positive to going in the 'off season' is it will be less crowded and you can really get some great deals on hotels and airfare.
The positive to going in the 'off season' is it will be less crowded and you can really get some great deals on hotels and airfare.