I think these are donkeys years old. You might be able to get some advice from the likes of

http://www.storageheater.co.uk

They helped me out big time 9 years ago with parts for a long-obsolete storage heater.

See also this thread from 10 years back

https://www.electriciansforums.net/threads/enviwarm.54758/

BUT for your own safety, before you do anything to it, read this thread,:

https://www.justanswer.co.uk/home-improvement/94uhd-enviwarm-hot-air-system-selling.html

Ghh
December 2022