Thanks everyone.

Jazzcnc, first I must agree that Yorkshire tea is the only proper tea, and I am a southerner too.

Good to know that I measured the ends of the ballscrews right at least.

With the ballnuts, I don`t think I have actually been having any problems with backlash and I am pretty sure the clicky noise is coming from the BK blocks particularly on the Y axis. I am only butchering wood with it at the moment.
So perhaps I will leave them alone, I was just thinking of doing it because I will be doing the ends anyway. I have a vison of loosing many tiny ballbearings over the floor if I try to dismantle them.

I will send you a PM.

Thanks

Ollie