Hi C2j
Just going to take a pot-shot at this, it sorta fits the clues, but not great!
The Rollason Beta of 1967 ??
Collaboration between British Aircraft Corporation (but ony trainees) and Rollason Aircraft and Engines (hardley be described as major players). Described as a Racer, placarded speed match OK and it was stressed to +6/-3G, it did have a stick and looks like a 'chute pan type seat. I found a photo of the cockpit, it doesn't fit great, but is is the prototype and they stated there would be changes in the following A/C, so who knows!!
So assuming I'm wrong, does your cockpit come from your side of the "pond" and is it before or after my shot?