At this time I was going to replace the pads and disks on the front and try to locate a noise/rumble/rattle from the O/S front corner - so off with the mudshields.
The noise was not the vacuum pump as I suspected but in fact the automatic tensioner. I think this arrangement is only fitted to the 2.5s with A/Con. The manual tensioner pulley is fine.
The bolt in the pivot had sheared and the needle bearing assembly in the alloy housing had partially siezed and the noise was the combination of all this lot rattling around in the housing it is (supposedly) attached to. Fortunately the sheared bolt stud screwed right through the housing and no problem with extracting it.
So I am in need of a complete new automatic tensioner assembly and aux belt, discs and pads.
There is a slight oil leak from the seal behind the crank pulley and I am uncertain whether to try and change or leave well alone. I will see how I feel when I have read the XM book of instructions
Keep smiling and ........................
Robin