That case was overturned almost a decade ago.
He says that feminist have wrongly said - about the Assange situation - "Sex without consent is rape". Let us let pass by the fact that, on that version, George Galloway is a feminist, since he "clarified" his first wrong assertions saying exactly that.
The law of rape is available to all, including yesterday's author, in the Sexual Offences Act 2003.
It says that it is rape if a man (A) has sex with either a woman or a man who does not consent and who A does not reasonably believe is consenting.
Whether a belief is reasonable has to be determined having regard to all the circumstances including any steps A has taken to ascertain whether s/he is consenting. (Section 1 ) However it also says that there is a presumption that there is no consent if the person was asleep or otherwise unconscious at the time of the relevant act. (Section 75)
On both bases, "Sex without consent is rape" as Galloway said, is a reasonable summary of the law when A's companion is unconscious.
Sleeping people cannot consent and what reasonable person could think that they can?
What has been discussed is some presumption of ongoing consent from earlier consensual sex but that is untenable since nobody can tell from a sleeping person whether they do or do not want to repeat the experience.
None of this affects the consensual nature of the earlier sex.
A's companion may be willing to have more sex but the only practical way to know his/her state of mind it to ascertain it at the time and that is certainly the lawful way to behave.