Again, my point is that although an act may be a sexual offence it is not necessarily rape.

According to English Law, the age at which a female is deemed incapable of giving consent would appear to be 13 years(there are several references to this). So, the offence would certainly be that of rape then.

However, between 13 and 16 years, it is not necessarily so. If the female is a willing party, it is a different offence.
Of course, it may arguably considered to be just as serious.