Brompton bike - one of first ever - collectors, vintage, rare, 1980s

Brompton bike. Condition is "For parts or not working".
Collection preferred. Delivery arrangeable
This is a vintage bicycle from the 1980's. It's 1 of the first 1300 Brompton Bikes ever made (as confirmed by serial number) - I'm told by the bike shop that it would've been made by the inventor and his team by hand.
This should be the first, or close to first version of the Brompton.
Great for a collector or Brompton fanatic considering its vintage.
It's currently not rideable - so best suited to someone with the technical know-how around repairing it.
Viewings welcome in Pimlico London. Can also send a video showing the bike in closer detail.
My history with the bike:
I bought the bike second hand in not the greatest of condition, spent 200 on getting it working (which it did, smoothly) and then eventually a screw popped out just by the bottom bracket (from which the rear fork/triangle swings) That screw pushes up against the chainring. Rendering it unrideable.
An explanation of the repair issues:
I'm not too clued up about bikes or repairing them and hoped it was an easy repair... That wasn't the case. I've been told a special tool is required to remove the part and fix the issue. Anyone who would want properly operating mini wheels for rolling when folded would need to weld a wheel on or replace the part. I believe it can be repaired but can't be sure. I've found the triangle part  for £200 but as I don't know how to repair it or the intricacies of what would and wouldn't fit, I figured this project is best left to someone who knows what they're doing.