My 411 has 4 distinct keys - ignition, doors, boot and fuel cap.
My keys all have numbers on them, except the ignition key. The doors and boot keys are Wilmot Breeden/Union brand.
I assume one way of solving the problem is remove all the locks and take them to a locksmith to have keys made. But I imagine that would be quite expensive.
This looks useful
British Car Keys
PS. My petrol cap lock has a Yale key.
This site also looks useful and they're in the UK
https://www.arun-locks.co.uk/products-and-services/
My boot key is single sides and the # starts with FS.
The door key is double sided and starts with FT.
I forgot there's a glove box keys also, mine is single sided and starts wit FS.