Ok, having gone through the Haynes, I think I've sussed the tensioner marks. I have to take the pointer beyond the final position by 7-8mm, turn the engine over a couple of revolutions, check the timing tools all still fit properly and if so back the tensioner off back into the middle of the static index. Which is what I've done! Happy to say it all seems timed correctly. It's actually quite easy when you've done one, and have the relevant tools, would be a nightmare without the tools!