How about Rumer Godden's The Greengage Summer? Somewhat similar voice (teenage girl) to I Capture the Castle but not quite as whimsical.
John Mortimer's Summer's Lease I fell in love with years ago though it's really not out of the ordinary...just makes me want to be in Tuscany...
...A Room With a View...
Elizabeth Bowen, Heat of the Day. (Okay, I haven't actually read that one. But I intend to!)
Something in Provence would be good.
Miss M.