Nigel Mansell World Championship-there's two Nigel licensed, a crappy one disk version, and a much better two disk version. I know most won't agree but on a fastish cpu like yours, its the best racing game for an A1200.
Deluxe Pacman
Arcade pool and arcade snooker.
Speedball.
And the king of multiplayer sports: Sensible Soccer, try the newest versions when you get good.
3D FPS: Gloom is fast, original Doom (ADoom is probably the best), Alien Breed 3 D, Nemac IV