All i did was to unbolt the three bolts that hold the turbo to the manifold, blanked off the turbo inlet and drilled and tapped manifold. I then fired up the engine to blast the swarf out. I checked the manifold was free of swarf, then removed blanking plate and refitted turbo. I fitted the probe with about 10mm of it in the manifold.
Since then I've checked all the feed pipes from the airbox, both pipes from the intercooler and flushed the intercooler, and checked the manifold was sealing onto the head.
The diaphragm linkage seems free enough, but I guess my next move should be to remove the turbo and strip both it's housings and inspect the linkage is free.
If anyone has any other ideas please post them up, this is something of a crisis with a camping trip this weekend