If it just you and the girl and you ask for hand relief she will either say yes or no, either way you are unlikely to get into trouble. If it's you, the girl, your mum, a member of your local constabulary, Jesus, and your wife in the room and you ask for hand relief you could reasonably expect some bother.
There is a forum you could go on where UK punters recommend a number of girls who will happily massage you then toss you off but for the life of me I can't remember the name.