Being one of those Shropshire types, I can confirm that you must be careful with the weather. Take today: no cloud, 30 degs, awsome vis but a 10kt wind. The turbulance over the top will still be rather rough. I've tried to do Sleap - Anglesey a couple of times but each time I have had to go the long way around because of the turbulence. Its probably not going to break your ac but the local soothsayers reckon you can only go over the top of Snowdon a handful of times each year without re-distributing your passengers lunch.
Valley AIAA - No problems at weekends.