In reply to simondgee:
I should have mentioned that I'm not based in the UK, our helicopters fly with only a doctor on board. If they need technical help for a rescue then they'll pick up a rescue specialist from the MR on the way. I'm not qualified to do that yet, but it's certainly a goal.
We get nothing from the teams, (not even a t-shirt) but there are small discounts available on kit. Looking through the list there was the standard chest harness (Edelrid) but I also noticed the Petzl set-up. Despite being very different it does say it's allowed on the helicopters, there's nothing in our SOPs about it though so I'll have to investigate how it's actually used on a winch.
@stuartholmes: funnily enough the Big Gun was also on my radar. I don't know anybody with one though, so I guess I'll order both, have a hang and see what I prefer.
Thanks for the feedback everybody.