I've not done any fettling of those in particular, but if there's a myriad of variations and it's not 100% clear what you need, I'd Strongly Recommend taking the original to Lumsden, where they will have every possible variation and the knowledge to advise.
There are other variations where there's no knob or key-hole on the inside at all; its integrated with the door handle, and is operated by cranking the handle upwards to lock, and downwards to unlock. Good for emergency egress. Depends how complex the mechanism is. As I say, not my area of knowledge, but very much theirs.
Also, I've found keys cut by them are approximately an order of magnitude better than ones cut in a random key kiosk.