Hi Phillip,
Some story! I hope all the bad luck is behind you!
I checked some USA resources and there are places to have custom sized radiators made. I’m sure searching “custom radiators” will turn up some sources in the UK.
Another possibility, armed with the dimensions, a really good auto parts guy/gal might be able to come up with a stock replacement radiator that would fit.
Paul Mossberg
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica Roadster
If you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)