You will be surprised how many makes they can do that are supposedly not available. From the impellor to the compressor to journal bearings etc, all can be redone so won't harm ringing them. They also deal direct with Holset and Borg warner so can get OEM turbo's too at very good prices.
holset dont do car turbos in huddersfiled, i know i work there its all big stuff for truck etc, we will be doing small turbos shortly but not for cars, borg warner do
as long as the castings are ok and turbo can be rebuilt is not rocket science, but the core may need to be ballance when new shaft n wheel or impeller are added,all our parts are pre ballanced and prob need to adjust 5% of them to be intollerence, its to stop vibration
on reading this thread id say the turbo is fine, sees the vg part may not be working correctly either with the vacum side or sticking moveable vanes, the garret design of vg turbo is flawed but its complex nature..........holset vgs are far simpler with sliding wall concept, and our newer one have electric actuartor so no pressure problems
poor engine servicing kills turbos, not changing oil regular or letting oil pipes get clogged starving the turbo of oil, internals tend no to wear if the oils good as the oils is the thing what keeps the shaft from touching the jounal bearings.
if pistons seals on the shaft go the turbo will still have power, itll just smoke !!
i love it when poor garages allways say its the turbo ......walk away n find one who knows about engines