I too advise going with the lie. For now.
Then you need to do some reading on controlling relationships and emotional and psychological abuse. You will find that lavish gifts and proclamations of love can feature as an abusive tool to confuse and disable the victim into thinking their controller loves them really.
Like I said before, if he was horrible all the time you'd just up and leave, so he needs to balance out his possessiveness with something twinkly and distracting...like a new car, shopping trips, words of depth and romance.
Interestingly, I note he uses those things to distract and manipulate, while further controlling you. "With everything I do for you you'd rather go out with your friends?" "I pay for everything!" "I just want to be with you, but you don't feel the same." "I love you more than you love me." "Boo hoo hoo...woe is poor, unloved me."
He fundamentally believes he is buying the ownership rights to your autonomy.
Once he has you distancing yourself from your friends (which you will and are probably doing already...you can't cook up lies like this every time you want to see them against his wishes. In the end you'll just stop bothering with them because it's easier than facing his wrath) he'll start on your family and anyone else he considers as being close to you and possibly having some influence on you or being a source of support.
Isolation is coming. It's happening now.
Once you're on your own with him, your life will be Hell. Mark my words.
If you don't believe me, or think I'm being melodramtic, do the research yourself.
And whatever it takes, go to that hen do - you want to keep your friends close and you have every right to, no matter what King Dick there has to say about it. It's not. his. decision.