I'm sorry you've had to go through a LLETZ treatment and that you're feeling down. I do feel for you because I also found it pretty horrific when I had it done. it's all a huge shock isn't it?
I'm sorry you've got a sore bum. I've had vaginal infections following procedures but not experienced. They use acetic acid (which is basically a medical grade vinegar) so I guess it's possible if it that leaked out it could soreness, although I'm no doctor. How would would you feel about going to see your GP and getting them to take a look? They might be able to recommend a cream or something to help you? That's probably what I'd do.
I hope you feel better soon, and it may be that someone will come along who has also experienced this. Take care x