Well I fitted a new cat, plus new gaskets ect, problem seemed a bit better, but wasn't resolved, engine seems happier with the new cat, and there definitely isn't a ridiculous amount of heat pouring off the cat anymore.

I Bypassed the HCV, and it sorted everything.
So now, where do I stand, the HCV is basically new, bought it new from fords ages ago, only fitted a few months ago.

The serial number is 7N21 18495 AC, on the model I have.
Not sure weather this is a new one or defective one, or what, but from what I've read, the 7n21 18495 AB replaced all the older 98FU models.
But not sure on the one I have.