I finally got a new belt and had a fight to get it on. Fired her up and the belt stayed in one piece, but the noise that the mechanic I paid 50 quid to diagnose was still there after replacing the PS pump (which he said was the source of the noise, and he offered to change for well over a grand). I'd also replaced the alternator and the tensioner. So only one place left to go - the idler pulley - and that was the source of the noise. Swapping that was really easy, the belt loosened easily when I jacked up a 15mm spanner on the tensioner. Unscrewed the old pulley and screwed in the new one with the belt in place. With the nice quiet aux belt and it's components I can now hear the hole in the exhaust much more clearly.
Last edited by TheLibrary; 28-09-14 at 21:21.