Baz,
What you have noticed with draglink movement is how it is on all of the roadsters. I think it is one of the things Ash thinks caused his ali adjuster to fail, by pulling on the draglink once it had ran out of movement.
Any nut & bolt supplier should be able to get the M18 half nuts for you. If not you can get them on ebay.
http://cgi.ebay.co.uk/M18-x1-5-RIGHT...item4153126238
Cheers
Dave