The Numax battery quoted by the OP has an MCA of 1000.

MCA is approx 1.25x cca so the battery in question is approx 800cca.

I've had two Numax batteries: one was excellent but the other was rubbish from day 1.

Well... I have just taken the plunge and bought one from me local motor factor....
It's a VARTA 630cca 70 ah. It has a 4 year warranty and was £70.00. Car started straight off this morning no probs.....decided against a mail order in case of problems occurring. I think it will be ok. I don't have winches and all that stuff (yet)...:beer2: