Sorry about the multifont post - looked okay on the ipad - but wrong on the PC.

Well thanks for the link to the bellows - that can definitely mitigate the risk of dust/chipping on the bearings.

Regarding buying everthing from BST - i have been expoilting some of the free postage offers they have had for the ball screws so almost have all of those, seem reasonable quality ( can only come to some SKF ones i used a few years back). I haven't been that lucky so far with import duty - and think that i will be financially worse off importing the rails from china. So back to my original question is there any reason why i cannot buy the rails and carriages seperately, my worry would be getting the carriages onto the rails if they are a very tight fit - i assume that a chamfer could be machined onto an end -to ease fitting.