Bought my previous 4 Morgans privately and the current one was ordered through a dealer from new.
Would buy an old Ford engined 4/4 privately secondhand again as I have rebuilt most of them. Enjoyed the experience and did very well. I don't count time and lost income when I am enjoying myself either driving or dis/assembling.
Not sure about Rover and Triumph but I am sure I could be convinced.
I think BMW

would have to be dealer.