Chris,
Start of your long journey of discovery about the A.C. Car: The Ace and Aceca do have adjustable steering stops on the front uprights and there might be room for a little more lock, but probably not as the tyres will likely contact the inner wheel arch panel. All part of the charm. The turning circle of cars in the fifties was not, generally, as we would expect from a modern vehicle. There were exceptions, of course, like the London Taxi and, later, the Triumph Herald, but not the Ace or Aceca.
Happy Motoring with your Aceca and do keep us informed how you progress
Barrie