4wd converted to 2wd

[2000rpm]

What reason could there ever be to buy a car with something like that then mot want it.

There isn't.

I'd walk away and find a fully working one for same price.

And if 4wd is wanted, look for one from 2011 onwards which should have less chance of problems with the 4wd.

However, it's possible that the car AdamLoughran is looking at simply needs a new diff pump rather than a new diff. That's several hundred pounds instead of a few thousand pounds.
With pump failure there will be the dash warning messages (service 4wd, service rear axle etc) but not the juddering during slow-speed sharp turns. Of course there won't be dash warning messages if someone has pulled the fuse for the 4wd electronics.
If it's just the pump that failed the rear diff might not be grinding itself to bits internally.

[2000rpm]

A quick search also suggests the vehicle's tax expired in January 2018 and MoT expired in September 2018.

[lizzard-t]

Thing is the op may of asked the $50,00000000 question at the wrong time , hopefully not and that he can do the moonwalk out of the car showroom still intact with his hard earned money ?

The reg number on that car is showing an insignia diesel ( as per Gov website )
Not a petrol as it's supposed to be .

[exclusiv.]

Personally,I wouldn't touch it with a bargepole,,,who in the right mind wants to disable 4x4 system,cos it's not needed