(Unless I'm severely wrong, have been lied to, and have researched in the wrong places) In the UK a penis has to be involved in non-consented sex/rape for it to legally be rape, whether the man is being raped or the man is the rapist there has to be a dick, a woman could force another to have lesbian sex and that's not considered rape due to there not being a dick, that's morally rape but not legally rape so pretty much...

Girl on girl rape: legal Guy on girl rape: Illegal Girl on guy rape: Illegal Guy on guy rape: Illegal

As long as a guy is involved it's rape