I did a quick google, and came up with very little. There's a con called Thought Bubble in Leeds.
Another list gives the ones provided above.
I would also say, if you're willing to travel, it's not that far to Manchester which has a lot of conventions in various parts of it, not just the big MCM one.
Also, Birmingham would be easy on the train.
I think through looking at this though, I've decided that there is a gap in the market, and we need one in center parcs to be able to run riot through a forest in cosplay.