He went upstairs and found the woman lying on her stomach and had sexual intercourse with her.
He then performed an additional act which the woman objected to, hitting his hand away.
Judge Winter said the jury found the sex was consensual but they found the intimate touching was not.
"The aggravating features are clearly the vulnerability of the female.
"She was feeling sick, she went to sleep in a bedroom away from the others. You took advantage of that situation and while her sexual intercourse with you may have been consensual, the intimate touching you did was not."
In sentencing Munton, Judge Winter said he had to keep in mind the extent of harm to the woman.
"It is difficult for her to separate the act of sex from the intimate sexual act.
"She has profound regrets of the evening, enormous embarrassment and is struggling not only emotionally but in her relationship with her partner and with her employment."
President of the Law Society Jonathan Temm said the verdict upheld the generally held view of consent.
"The jury decided this kind of conduct was not something a woman would consent to, while intoxicated and having never met the person before.
"Even if someone has given consent, they can withdraw that consent at any time. When the consent is withdrawn, any conduct that follows is culpable conduct."