I'd also give Tony Castle-Miller a try at Middle Barton Garage in Oxfordshire, GB. He supplied a wealth of information (for free I might add) and parts for the first part of the running restoration of my Stradale, including drop links and suspension settings for the car, so I'm sure he'll be able to help.
I only hope that he hasn't been too badly affected by the current flooding as West Oxford has suffered quite severely.
Tristan, I assume you're talking about Andy H's car. Andy already has a working relationship with GM as I believe he has recently purchased a 130 Coupe from Guy - so the direct personal approach might pay dividends.
Please let us know how you get on as I'd be interested to see who can supply the right part for the right price
Cheers
Simon