Hi Gary, we were both pleasantly surprised when we test drove the cooper D engine too. So much so that we bought Broadoak BMW demonstrator including s few toys. My wife is the proud owner of a 61 Cooper D convertible; great little car.
This was the 1.6 PSA (Peugeot Citroen) diesel unit. Always wanted to get it remapped because you can take the engine to about 165bhp pretty easily. BMW heavily detuned them for some reason.
It was the cheapest to run and most reliable car I've ever owned. Set of rear brake pads, and a turbo seal which cost less than a tenner in the whole time I owned it. Eventually swapped it for my current Z3, and a cheque from the dealer.
I can remember the test drive of one at the MINI dealer in Swindon. I really wanted to get a 118d, but had a bit of an itch to at least try the Cooper so arranged a test drive. Told the salesman I wanted to hate it and that I was going to go and buy a 118d instead (I had a 120d as a company car for 50k miles).
Was honestly blown away by it, and halfway through the test drive I called the salesman a rude name and told him I was going to get one. They didn't have one I could afford at the time, so I got this one from Exeter MINI.