Kye,
again thanks for your reply and investigations. Especially "Kirby-Lauson", I'm sure you're right as the space is there for the "Kirby" (and Jack told me it was a Kirby). Jack also came up with very similar advertising results.
In fact I have Jack to thank for encouraging me to go back and get it. I'd sent him a photo and was ummm-ing and ahhh-ing. In doing so I picked up the catcher as well. May still get into trouble yet when I take it our of the boot at home...
Good news is I have a mate at work who knows a bit or two (or more) about mechanical things... He's had a look at it and thinks the internal damage *may* just (hopefully) be the piston (+/-) conrod so it *may* yet work again if I can source parts. He also thinks the base can be fixed (welded).
My repurposing is simply to take the engine off and bolt a box on for my daughter to push around in the garden. This shouldn't require any damage so the base will remain salvageable. I can look at the engine in the meantime. If it all comes together we may have a working mower sometime in the (possibly very distant) future.
Dunno that it may ever be worth much more than curiosity value. I suppose sometimes the 'value' is in saying, "I got one, do you?!!" (?)

Still learning (a lot!)
Cheers,