Hello and welcome back!
I have an idea on where you could find the parts and services.
Have a look on ebay to see lockies selling Chubb or AVA blanks, they more than likely also have the discs.
Here's an example of a cut key with the levers for it included as a bundle:
https://www.ebay.co.uk/itm/186538099892 perhaps Contact that seller in Watford and ask if they have the AVA mechanism discs.
Here's an ebay locksmith shop from Birmingham, West Midlands saying they can cut your Chubb AVA key from a photo, so they must have some experience (and hopefully parts and discs) they may also be able to sell you, or even rekey the locks for you.
https://www.ebay.co.uk/itm/385499721810Good luck and thanks for your post,
Squelchtone