Nemesis runs fine in ZXGP32. You can map the 'B' button to the correct keyboard button for selecting options.
I was too lazy to find out which was the correct key, so I just mapped button 'B' to space, selected Sinclair 1 joystick and then redefined the keys within the game and pressed the appropriate direction/key as all worked fine.
That said, that specturm version of the game, as WhizzBang said, is rather pants.