I agree about Solent, without doubt the most helpful controllers in the South of England. Last year I'd carefully planned a route around their zone, and was actually offered a crossing clearance I'd not asked for - now there's service!
But, I've never yet been refused a crossing clearance from anybody, asked to change height or route a bit occasionally, but I can't say I've ever failed to get what I ask for. Having said that, without a doubt, some controllers are more helpful than others. My normal whinges are about the level of RIS I get, which is very variable (and again, Solent is without a doubt the best).
G