Thanks Amtrapid

I put the new tensioner on today and it could barely move 1mm left or right.
But it seemed to be all the way over to the right looking at the bolts relation to the slots. So i ground the housing a little, now it will move about 3 or 4mm to the left. That should work as it will move a similar amount as the old tensioner but without crushing the lip.

On another note my cam wheels seem to all sit still and line up freely with no tension on them. The book seems to imply the left cams will be on lobes and need to be held in place, is this normal.