Re: Nuffield health.
Probably the best thing is for you to walk in there and ask to have a look around and decide for yourself.
My experience is no, it is not worth it, - I found their gym lacked equipment which was the biggest deciding factor for me... my current leisure centre is far better equipped, and cheaper! I also saw a physiotherapist there once (via private health insurance) and I wasn't impressed with her at all.
I used to walk into a room full of people & wonder if they liked me..... Now I look around & wonder if I like them