correct Garnz!
Only thing you could do maybe is argue with the DVLA and say that it should have been on an "N" plate as that was the 1st N15's over here.
The reason it will be on an M plate is whoever imported it will have declared the year of manufacture as 1995;
M 1 AUG 1994 - 31 JUL 1995
N 1 AUG 1995 - 31 JUL 1996
They should have said (as it would have been) after the end of July 95, making it an N plate.
Worth a try Stu!