Development cars do get sold off i mot'd a grey mg zr on a q about three years ago it had done 1230 miles an on a Q plate it was an early shape one probably made circa 2000/2001, however the vin number was only 12 digits long not the usual 17 and never registered with the dvla.
The guy who owned it bought it from a liquidator who was selling stuff from the longbridge factory the car came with a little bit of documentation to say it was a development car for mg rover and not for retail, The guy paid £1700 for it applied for a log book and because the date of manufacture could not be established was put on a Q, next stop an mot as its classed as a 1973 car then road tax and on the road.
The guy who owned it did some research on where the car had been and it turned out that the car along with another seven had been in a lock-up since 2002 which was leased by the mg rover group.
He did have the idea to try and get the car on a private plate and was told that the Q had to stay on the car unless he could get documentation from the manufacturer stating the exact date of manufacture, as the 12 digit vin was a development number with no reference to a date this was not possible.
However he did end up with a brand new car for £1700 which he was going to use as a daily hack till it would not go anymore.