Thanks for the recommendations, I've gone with Steveg's recommendation of Garland Cycleworks who are the local GreenSpeed dealers.
The opinion there is that it may
be possible to bend the rim back into shape and then hold it with the spokes. I should know by lunchtime tomorrow if this is going to be feasible, or if a new rim is urgently required.
Either way, with any luck at all, I should have the trike back in commission by SwanCon
. Oh, and yes, I'm still shamelessly pimping for suggestions and/or copanellists for the Anime Archetypes
and Rocket Boys