Unsure of the law in England & Wales, but in Scotland a woman can not rape a man as the law states there must be forced, un-consented vaginal penetration. Anything else constitutes sexual assault which carries a lighter sentence.
Indeed, the mens rea is "the intention to have intercourse with the woman without her consent" (Jamieson v. H.M. Advocate)". Interestingly, the law also states that post-op transexsuals can not be raped nor can they rape. This has it's background in history where it was thought that going off with a female and defiling her was of a greater offence to her husband or father than to the actual female. Indeed, it was stated in a court case that the consequences of rape were "the danger of impregnation - the loss of status, - the taint to her family (Sweenie case)". Though of course this is now outrageous and not supported.
The Macra or Macrae case ruled that penis penetration must occur, even if it is slight.
Barbour v. H.M. Advocate (1982) ruled that oral or anal sex does not qualify as rape. This would be covered under indecent assault legislation.
What legislation is that? I assume it's the law that was passed last year, and comes into force at some point this year though I can't remember what date. I forgot about that until you mentioned it. Haven't done any sort of criminal law in over a year...
Sexual Offences (Scotland) Act 2009 has come into play already. I forget the exact date but now sodomy (the old crime) and oral sex is classed as Rape (and so it should).
Penetration with objects other than a penis e.g. digital penetration (hand/fingers) is considered "sexual assault by penetration"
More info here - http://www.oqps.gov.uk/legislation/acts/acts2009/asp_20090009_en_1