Blimey, you lot like your research, don't you!
I've only read about two-thirds of the thread, but getting back to one of the T280s in particular, I've asked some pertinent questions and can perhaps confirm or fill in some minor details about it.
The car that ran Jeremy Lord raced in the 1974 Tricentrol Championship was bought by Minilite from Heini Mader, who had indeed looked after Jo Bonnier's cars. It was described as ex-Jolly Club and the name Giorgio Pianta apparently rings a bell. As delivered it had the drop-down bodywork at the rear and the central cockpit division, but not the full width roll-over bar. The roll-over bar was extended and the central division removed in order to comply with then current FIA regulations. The front splitter was also a Minilite addition. The car was maintained and run by David Price out of his lock-up garage.
The car did nothing in 1975 after Minilite and Lord withdrew from racing, but had one last outing in their hands at Silverstone in a 1976 meeting, which it won from Willy Green in a Ferrari. Then it was sold to Jorg Zaborowski to race in the Interseries.
In due course it found its way back to the UK and was bought Marsh Plant Hire and raced by Ray Mallock and John Cooper in Thundersports races. Ray put the rear wing on the car and modified it quite a bit. I've seen a video of them winning a race with it on the Brands GP circuit in 1983. Very exciting race, actually.