I'm working tonight - Friday night - from 7pm till 5am. Much better than 8am. After that I'm not going to work till the end of the month (my weekends are pretty full at the moment) and then after the summer holidays I'll be signing up for one day-shift a week. I think I can make this work. If I work only one day a week, I think I can almost double my income without it effecting my day job.
I'm also going to look into registering for tax, and (unrelated) I've decided to move house. I'm now really looking forward to next year. I think life has just got a whole lot better.