Rather surprisingly it didn't jump a tooth at all - when I pulled the tensioner tight and locked the crank the cam bar was just a mm or two off fitting in place. The belt had been fitted by marking the pulleys rather than using the proper tools. Its amazing its not completely destroyed tbh. POs have been driving like that for up to 5000 miles since the belt was done.
I've got a £100 ebay tensioner on the way to test. If I get compression on 1-4 with that in place (and the cam stops jumping about) then I'll spend the £500 on a genuine one from TPS. If the valves are bent or there is other internal damage then I'll be looking for another engine and I've only wasted £100 instead of £500. The engine is out now anyway, since its utterly impossible to get to that rounded off oil cooler bolt with it in the car. I'm going to do a complete re-seal on everything and clean up the bay while its out, and I can compression test it on the floor.
This car is like a mistreated horse - its now kicking the crap out of anyone who comes in range
