I wouldn't turn back.
Autothrust u/s is dispatchable per A330 MEL. See below:
22-30-01B
(o) (m) (T) May be inoperative on both engines provided that:
1) ETOPS beyond 180 min is not conducted, and
2) All thrust lever position sensors are checked operative.
(o) Refer to OpsProc 22-30-01B Engine Autothrust (A/THR)
(m) Refer to AMM 22-30-00-040-802