Hello,
criminal barrister here who both defends and prosecutes in rape and sexual assault cases with variously male and female complainants, and male and female defendants.
Anecdotally, and speaking generally I really would say the following:
The law basically prohibits questions on sexual history where the questions are designed to suggest the complainant would be more likely to consent BECAUSE of that sexual history.
The law allows previous convictions to go before the jury is they show a propensity to commit crimes like those being alleged.
The law even allows previous acquittals to go before the jury in certain cases - in R v Z 3 previous acquittals were put in evidence before the jury where the defence was reasonable belief in consent. The point was someone whose been tried for rape 3 times in the past ought to take a heap more care in making sure another person with whom he is having intercourse is really genuinely consenting.
Having said all the above,
it is a really difficult crime to prove. There are rarely other witnesses and this makes juries uneasy as we know people do lie and false complaints are made. And when the burden is on the Crown and the jury have to be sure that is a high standard to meet and with the best will in the world one person's word against anothers may not be enough.
Also, and this is the Helena Kennnedy point, women judge each other. I think, fwiw, it's a way of us making ourselves feel safer. It is such a vile crime and one of the most frightening things we can imagine, we do not like to think it could happen to us, even though we know this is the case. So we look at the facts we are presented with and say, this wouldn't have happened to me - I would never have drunk so much/gone to his flat/given him the wrong idea/worn that outfit. If asked simply - do any of these factors mean the rape was somehow her fault we would clearly say No, but even so we look for ways to reassure ourselves we would never go through such an ordeal. And that makes us pass the blame away from the perpetrator and start to judge the victim. It's not right, but we have to find a way of teaching our children to take responsibility for their own safety at the same time as holding predators to full account.
Finally, and this is perhaps the most controversial observation - the consequences are so horrendous - both for sentence and public disgrace, people even if satisfied the facts are against the defendant, sometimes may not convict because they are sure it won't be done again - (s)he may seem respectable, ashamed, supported by a loving partner. I have seen what I had thought to be overwhelming cases not succeed where the only possible explanation seemed, however mad this may sound, the likeability of the defendant - especially if alcohol was involved on both sides.
Sorry for long post, but I had a lot to say....