Most helpful in my experience is Solent Radar, they routinely go out of their way to offer clearances or information that might be helpful, even if you never asked for it. Several times I've declared routes around their zone to be offered radar control through it, saving me a fair bit of time.
For the light aircraft pilots amongst us, the chappie in the tower at Sandown IOW is ceaslessly cheerful - even when I rang on a mobile from a field next to the M3 to cancel my PPR!
G