Don't panic mate... My cam bearings were worse.

After advice from both stu and Karl, I gently dressed the bearings and caps off wit 1000grit, then built them up again.

I think what Karl said was to do this, put it back together without tappets, then see if there was any play in the cam bearings. If not, then it's all good.

It's probably picked up on start-up the last time the cams had been out.

I reckon its caused by the shape of the cam bearing - it kind of wipes the oil off as the cam turns. When I rebuilt it, I filled the engine by pouring oil directly over the cams before putting the cover back on

Neil.