I'm not versed in UK law, but live in the UK and am aware of a few cases. Bottom line - British law does not recognize the possibility of consenting to actual bodily harm.
I'm not aware of any recent case where the person on the receiving end was prosecuted for consenting, perhaps the OC can cast some light on that.
My acquaintances mostly reference Operation Spanner which is about 30 years old now. I don’t know if that counts as recent or not, however while the Law Commission recommended in 1994(!) that this law be altered, it appears their recommendation was never adopted.
I'm not aware of any recent case where the person on the receiving end was prosecuted for consenting, perhaps the OC can cast some light on that.