The reason the car wouldn't start was because the steering lock was locked on. Just need to know if it gets stuck again the best way of unlocking it.
usually, if a steering lock is sticking, just rocking the steering wheel as you try to release it should work.
edit to add...
and the usual reason it may stick, is turning the steering wheel after it has been parked, when the pawl engages with the column, but the tyres are still trying to spring the column back to where it was.
Thank you, Gremlin, that is exactly what I did. I don't usually use the steering lock. I think my seat is not in it's usual position and with a thick coat on I must have caught the steering wheel as I got out.