Which airport are you using?
In early spring you may want to stick to the SW corner of England, it tends to be a bit warmer and spring comes a couple of weeks sooner but there are no guarantees. Ive had a perfect week of riding in April, but in May it snowed.
I am in the East whch is a tad cooler, drier and flatter.
If you are in Norwich, you can get a round in at the Fat Cat
http://www.fatcatpub.co.uk/