You know what, when friends ask for a reason when I say no, they then get all upset when I say, I don't fancy it, or sorry not my thing, can't think of anything I would want to do less, sorry that friend you mentioned you are inviting make my teeth itch 
Not really, but I would rather just say no.
It is never a reflection on the host but I am not a spa, baby shower, knitting bee, book group, high filuting dinner party type of gal.
I do like a BBQs, dinner party with like minded piss heads and a vat of spag Bol.
I if I have said yes I will come, if I have to cancel and to be honest because I am honest in the first place, is a really rare event, I will give a reason and a bloody good and honest one.
Once and once only I cancelled on a friend because I was exhausted really tired, she was fine with it because I am not flaky she knew I was just done in, as I have been to parties when tired knowing most times I would perk up, this time I just knew I would be a miserable fucker, I was in bed by 6.