Thanks for the info jhitsema.
I think I will get them then, and carefully check them over and clean with some alcohol. The price isn't bad for me, since a 12A Emax is £10 compared to £12 for a KISS.
Going from Turnigy Plush to BLHeli blew my mind, the performance difference was substantial, hopefully the regen breaking and oneshot can do it again.
I think I'm set on the Sunnysky X2207S 2100kv w/ 5 inch props. Warm up on 3s and then racing on 4s. Will probably use Gemfan 5030 to start and then move to HQ5040, if I feel I need the speed