It looks as if radiofrequency ablation is very similar to laser treatment for varicose veins (I found an internet heading where both treatments were mentioned, and when I took a look, both descriptions were similar.)
I had one leg lasered in August. It was fab. By that, I just mean I was really, really impressed. It wasn't fun, but it was very bearable. I'd had a couple of veins removed nearly twenty years earlier, the 'old' way, and the laser treatment was so, so much better. The worst bits were the pain of the laser burns - but each time it happened, it only lasted a second or two - and an unpleasant feeling when the wire or whatever it was which was fed down the vein, was pulled out again at the end of the treatment.
I don't think you'll SEE anything! I lay down and a sort of table tennis net thing was put up at chest level so I couldn't observe the gore. I also had a really nice jolly male nurse jollying me along as the procedure went on.
Honestly, if you're going to be chopped up, I think these new varicose vein treatments are probably as un-upsetting as surgery can be, really. And it's just amazing, straight afterwards, to be able to get up (your leg/s will be bandaged, though) and WALK OUT and get a cup of tea and a biscuit on the NHS. You could even walk home, if you live nearby. I got the bus!
Don't worry too much, I'm a great wimp and I found it OK. 