Bit of an update for those that are interested,
I managed to blag access to a proper code reader and get this Jag plugged in to see what's what.
The Mass Air Flow fault turned out to be just me leaving it unplugged by mistake, so easy fix there. The Turbo issue is I think a well known problem with the variable vane actuator, which has dodgy solder joints to the motor that controls the vane movements.
Soo, I had a crack at resoldering it myself.
The bits that need resoldering actually look fine, annoyingly. I was hoping to see signs of a poor joint like burning or something. Maybe the unit itself is faulty?
I had a go at it with my ALDI gas soldering iron and ran out of gas half way through. Inexplicably Mrs Lankytim decided to bin my can of lighter fuel so I couldn't top it up so had to refit everything as is. I'd made a pretty poor job of things anyway and was expecting it to not work at all now.
Amazingly with everything back on the car it started and idled perfectly with the actuator arm now moving as it should as the engine was revved. A quick test drive and everything seems to work fine, although the limp mode light came on once but could be reset.
I left it for a couple of days before starting it again. It fired up fine but the limp light came on a few times before going away when the engine was hot. Maybe I need a new/recon actuator.
The pump and injectors seem fine, which is a massive plus. Perhaps this is going to e an easy fix after all?