Thanks for all the great replies! Yes, my avatar is the Cantilever Stone on the Glyders in Snowdonia. I used to spend most of my weekends in North Wales in all weathers and all seasons, aside from occasional forays into Scotland or sometimes even further afield. I hadn't thought of the link to my present post about a damaged cantilever until it was pointed out to me though!!
I have contacted my house insurance company and I may be able to make a claim. They have requested I get a report of repair costs plus a statement regarding how this may have happened?! I think they are trying to distinguish between accidental damage and wear-and-tear so I'm hoping this may be possible. Obviously I'll need to get the deck to a dealer and I shall be trying to arrange that in the morning but it may take a little time.
Suggestions of alternative cartridges are still of interest in case my insurance company does not recompense me (and after the excess and travel costs etc, not to mention increased future premiums I'll still be paying out - but I guess it was my mistake!).
I have used the services of Cymbiosis before and wouldn't hesitate to recommend them to all and sundry, but they're too far away at present. Upgraded sub-chassis and/or arm swap will have to wait awhile, but maybe someday....
I'll report back when I have an outcome to the insurance claim.