Your reconstruction is so close, I'm a little surprised you didn't stick with the original controls! Even though the BBC had a rather weird layout for all the non-alphanumeric keys.

It's been a very long time since I played Thrust, and I've played plenty of WASD games in the meantime, but it still felt really strange to control it that way rather than the classic BBC Z/X/*/? for left/right/up/down.

Pretty sure it was return to fire, space for shield/tractor; and maybe * for thrust? Edit to add: ah, no, shift to thrust. Works very well on modern keyboards too.