Thanks to Dave Mees, one of the Accucraft Service Agents, I have been able to offer the SCAC47 Chuffer, with the instructions below. You will see that this is not an easy fit as it needs a lathe to bore out the chimney which is supplied as standard with a 5,5mm bore.

 

You will find a list of Accucraft Service Agents (who can do the work without affecting the warranty) here:

https://www.accucraft.uk.com/repairs-services/