This turned up for me today, a manual adjust timing belt tensioner for the blacktop engine. The standard one is an automatic adjust item and just doesn't look up to job.

Cross reference the numbers on the back of the tensioner, looks like its a old rover tensioner, with a spacer pressed onto the back. Should work a treat!

If anyone wants one, email Ian Howell on  tech@fiestafrenzy.co.uk. At the time of writing cost was £45 + P+P