T5 turbo replacement

[Umai Naa!!]

Also check for a cracked exhaust manifold around cylinder #1 runner at the flange.

[Rebuild]

Turbo limp mode
Diagnosing and Fixing Limp mode for A4 1.9TDI - TDIClub Forums

Does the vehicle require oil topups between services?ie. is it using oil?

Stuck vanes by themselves do NOT necessarily require a rebuild/replacement turbo.
You have many cheaper options, depending on your mech ability.
1.I have found you can easily check for full vane movement by using a long screwdriver or similar over the back of the engine and press firmly on the actuator lever between the intake and outlet compressor wheels, until it reaches a hard stop.Doing this a few times may even be enough to free up the mechanism.
2.You can chemically clean the vanes.I have done this on mine with no ill effects, with Mr Muscle oven cleaner.You have to remove the exhaust outlet pipe though.You can also check for bearing movement
See here,
Chemical cleaning for turbo vs removal? - TDIClub Forums
3.Don't drive a variable-vane turbo diesel like a granny.Give it an Italian tune up once a week or so.