Hi - Thanks for your responses. Helping me feel right at home. The reg number is LPF 994D for those thinking it looks familiar. Those tools mainly for show - big hammer kept firmly under wraps (for now at least). Fourex, thanks for heads up on Australian forum too as it looks like another goldmine of information.
Stuart, good to hear you don't think it's a hopeless case and that someone has come through worse and is looking forward to doing it again. My plan is to ride it more than show it but I did see a picture of that M10 on display in Fort William and it made me think "what if". My main memory of riding it is the noise (yes v revvy) and the big step between second and third. I mainly used it as a grass tracker as soon learned that going over oil drums, etc, was harder than the experts made it look. Great fun to have two to compare, I bet.
So now on the hunt for parts. I probably need an engine overhaul. Tank is in reasonable condition. The top yoke has been welded, along with the bottom of the left fork leg so it would be good to find replacements. I did see a set of Mark 3 Matador forks and clamps on ebay in America which look as if they would do, but not sure how you find out apart from appealing to the these forums. There doesn't seem to be workshop manuals or parts lists easily accessible to buy for these early model (my Haynes is 1972-75). And most of the pictures I've seen of M10s have subtle differences so not sure which is the definitive "original" even if I did want to copy it. I think I need to aim for good enough rather than anything too perfect.
Will create a new forum post when I stop thinking and researching and start actually doing.