Golden Cup, I am sure of my facts, I have researched it thoroughly. The law on consent in UK is very complicated with minor differences between England/Wales, Scotland and Northern Ireland. "Anyone trying to have sexual contact (including touching) with anyone under the age of 13 is committing an absolute offense and can be served with life in prison". This the legal definition of paedophilia. After that it becomes a little grey.
"It is an offense for a male over the age of 10 to have sex with a girl between the age of 13 and 15 unless he can validly argue, he thought she was 16." Bounty comments - Plausible at 15, less so at 13.
"A girl having sex under the age of 16 is not committing an offense."
There is no legislation currently covering sex between a boy under 16 and a girl/woman over 16, however in some circumstances the woman can be charged with indecent assault. For example a 40 year old teacher and a pupil. If the girl is 16 and the boy is 15, prosecution is unlikely, particularly if it is consensual and a relationship.