Thanks eddy,yes I use toolstation for a few things because of price and proximity.I can now confirm that a 1605 ball nut has 17 ball per circuit as does a 1610,no idea why mine had one missing,it happens.I think i'll be using Wurth lithiun grease as i've a big tub of it from when I use to work for them(a sample,honest)again thanks for all the info.just putting finishing touches to a siegsuper x2 with help from Clive on the electrics and hope to post report soon,its only taken 6months or so..as it does:-S