Merpati Vanguard
You probably weren't hallucinating, I seem to recall that BEA sold at least one to MNA, and that it spent a few days parked at Birmingham (why I can't recall) with it's UK registration and in full Merpati scheme. I can't confirm exactly when, but around 1970 I would think.
Another poster will probably be able to confirm which airframe, and whether it actually flew for BEA in MNA colours.