Fact is Ste, if you are in the doghouse, you have no chance of getting out of this one bruv.
Swallow your pride, get an outfit and go to the party. Who knows, you might even enjoy yourself and would probably earn you brownie-points to boot.
It's a win-win if you go.
I was going out with a mate last Thursday, which Mrs Flash was aware of and had been arranged a couple of weeks beforehand. Two hours before I'm due to meet up, she text me saying "If I didn't want you to go out tonight, would you still go?". Now normally, I'd probably have kicked off about it but instead, I replied saying it was a bit shitty to cancel so late, but if she didn't want me to go then I wouldn't. Her response? No, that's okay, was just checking. Result: In the good books and got me some lovin' on returning home from a top night out.
Moral: It pays to show the woman in your life that you're thinking of her.