I just received a reply from the factory through my dealer about stage 2, and stage 3 performance upgrades.
Stage 2:
stage 1 + Cam's, Throttle body, Ecu. Adds +30 hp more. £2500
Stage 3:
Stage2 + CNC over ported heads , Cam's, Throttle body, Rockers, Ecu. +50 hp. £9,795.