To me, Sienna (Italy) is beautiful in March/April. The weather is nice and cool, there is no such thing as a horizontal street--up, down, UP, UP, UP, down, down, down, up, down (lol)--the history is awesome, the people are wonderfully inviting and friendly, and the food & wine are AWESOME! The countryside is to die for, the arts, crafts, historical sites....there is always something to see & do.
I would not consider it "British weather" at all, not at that time of year.
If you're looking for a relaxing time, good wine, good food, good people, and a little exercise via "exploring," Sienna is a wonderful choice.