Vinny's link is most appropriate, and there shouldn't be any dispute about your sexuality because you had already established that with your civil partnership. However, as already posted, UKBA appears to have acted correctly in dealing with your case, and in fact if you left the UK after the breakdown of your relationship and then re-entered on the same visa, you could be accused of entry by deception - but that's unlikely to happen.
However, to support your case to remain in the UK on humanitarian/asylum grounds, you could start by reference to the UK's own advice on the Foreign Office website:-
http://www.fco.gov.uk/en/travel-and-liv ... rica/benin
Scroll down to 'Local Laws and Customs' and see the following:-
"Homosexuality is not accepted in Benin and sexual relations between members of the same sex are illegal."
Go and see a properly-qualified Immigration Advisor or solicitor to help you put your case together.