I’d wait until after your op hun, you dont wana have the fuss of having to take care of your hair when you’re recovering!
I’ve always done my own extensions so can’t really comment on what to use etc as I’ve only ever used the same product.
Funnily enough I was just watching the Saturdays thinking hmm shall I have my hair cut like Frankies again? Lol but it’s taken me more than 2 years just to get it back to shoulder length, so I think I’ll grow it haha! xx