MDG - Do it. You'll be fine. I've taken DD away on her own, with just me, to Thailand, Australia, Fiji, Italy, Germany and Holland, from 10 months old (so had to deal with bottles/weaning/sterilisers/foreign languages - a couple of hospital visits while overseas, broken bones but have dealt with it all by myself!).
It's a worry the first time, but if you stay in the UK and go somewhere like Haven or CentreParcs it will be fine.
I was alone with DD (5) in Fiji last month and I think every other person there was in a couple. So what? My DD had so much mummy time, was just about the only child not in kids club, and we really enjoyed each others company. I honestly would never give a stuff what other people are thinking.
Please go and do it. Once you've done it once you'll be fine. There are also plenty of single parents around too, often at places like Haven and Centreparcs.
Please go off and book something! Actually, I'd be more scared of the bank holiday prices than going away tbh!