Welcome to the forum. Parts should be available there are a number of suppliers including Meetens, speak to Paul. I have manual / parts list for the 2a which I can scan and e mail, just drop me a personal message with your e mail address.
It is a small world, I was born at Highworth and lived at Stratton St Margaret before moving to Somerset. Know the lads at Haskins well as I went there for Land Rover parts. Also know Colin Hatch from college days.
OK so long as it is referred to as that site or similar and not named specifically.
The Mk25 is a 4 stroke and the 25c a 2 stroke, both were fitted to the Allen Scythe.