Yes, I know this is a long post, but you can always scroll down if you want to skip it. 
I think it might help clarify some things that are being argued about on this thread.
To expand on what dittany wrote about the law on rape, I thought it would be helpful to actually quote a bit more of part 1 of the Sexual Offences Act 2003, because it not only defines rape but also defines consent.
section 1 Rape
(1)A person (A) commits an offence if?
(a)he intentionally penetrates the vagina, anus or mouth of another person (B) with his penis,
(b)B does not consent to the penetration, and
(c)A does not reasonably believe that B consents.
(2)Whether a belief is reasonable is to be determined having regard to all the circumstances, including any steps A has taken to ascertain whether B consents.
(3)Sections 75 and 76 apply to an offence under this section.
(4)A person guilty of an offence under this section is liable, on conviction on indictment, to imprisonment for life.
section 74 Consent
For the purposes of this Part, a person consents if he agrees by choice, and has the freedom and capacity to make that choice.
section 75 Evidential presumptions about consent
(1)If in proceedings for an offence to which this section applies it is proved?
(a)that the defendant did the relevant act,
(b)that any of the circumstances specified in subsection (2) existed, and
(c)that the defendant knew that those circumstances existed,
the complainant is to be taken not to have consented to the relevant act unless sufficient evidence is adduced to raise an issue as to whether he consented, and the defendant is to be taken not to have reasonably believed that the complainant consented unless sufficient evidence is adduced to raise an issue as to whether he reasonably believed it.
(2)The circumstances are that?
(a)any person was, at the time of the relevant act or immediately before it began, using violence against the complainant or causing the complainant to fear that immediate violence would be used against him;
(b)any person was, at the time of the relevant act or immediately before it began, causing the complainant to fear that violence was being used, or that immediate violence would be used, against another person;
(c)the complainant was, and the defendant was not, unlawfully detained at the time of the relevant act;
(d)the complainant was asleep or otherwise unconscious at the time of the relevant act;
(e)because of the complainant?s physical disability, the complainant would not have been able at the time of the relevant act to communicate to the defendant whether the complainant consented;
(f)any person had administered to or caused to be taken by the complainant, without the complainant?s consent, a substance which, having regard to when it was administered or taken, was capable of causing or enabling the complainant to be stupefied or overpowered at the time of the relevant act.
(3)In subsection (2)(a) and (b), the reference to the time immediately before the relevant act began is, in the case of an act which is one of a continuous series of sexual activities, a reference to the time immediately before the first sexual activity began.
section 76 Conclusive presumptions about consent
(1)If in proceedings for an offence to which this section applies it is proved that the defendant did the relevant act and that any of the circumstances specified in subsection (2) existed, it is to be conclusively presumed?
(a)that the complainant did not consent to the relevant act, and
(b)that the defendant did not believe that the complainant consented to the relevant act.
(2)The circumstances are that?
(a)the defendant intentionally deceived the complainant as to the nature or purpose of the relevant act;
(b)the defendant intentionally induced the complainant to consent to the relevant act by impersonating a person known personally to the complainant.