Ooh, I forgot to report back!
So, they're great, although located in the middle of nowhere, which is slightly odd! but at least parking is easy.
I'm still going, had some Personal Training from Jay, and also joined some of the Team classes. I'd definitely recommend them. Proof is in the pudding with a parkrun time only 7s off my all time PB last week.
On a related note - is anyone here using Crossfit huntsman? (Not something that came up in my class searches before, probably doesn't hit the hertford keyword for some reason. They should probably fix that!)