//I also think we know that it's a ridiculously broad / ambiguous question with so many variables it's not likely to get a sensible answer.//
If you can't narrow it down then stay out of it Zacs-Master. It's not a broad question at all. Men have Viagra, women do not.
Tinkerbell I have asked various doctors this question and none of them have given me any kind of help. Thankfully after a number of years my partner finally sort of understands, but it's a mental strain on both of us and a physical strain on him.
I don't believe in herbal or homeopathic remedies for this, as my hippyish doctor would have suggested them by now if they even stood a chance of working.
If you find anything, let me know.