Turbo actuator failures are not exactly a known fault on the 1.0 TSI, but neither are they unheard of. It is possible to replace just the actuator, as far as I’m aware, but given the figures involved ...
If it were the actuator that has failed again I would think you had a strong claim for a replacement. The part that was fitted has a warranty, and if it has failed, the warranty on the actuator should ...