Cheers for the comments guys. The Marys do look good. I'll have a scout around on the on-one site.
I think you're right on the tensioner. It's a 40/20 ratio, which seemed to be be just the wrong combination to get the chain nice and short. I wanted to use the 'push-up' on the tensioner, but there was still slack at max push, so had to go for pull down - looks like it needs a bit more pull. Though if too tight, it pulls the chain to the side of the roller and it rubs. Next weekend's job.
J