Hey thanks for all the help guys. Out of desperation I imaged a new floppy (overwriting the existing one) and it failed with a bad sector. Created another disk on a fresh floppy and it worked and the game boots!
Don't know why it never gave any indication of a disk fault when trying to load before but sorry to have wasted your time when it was my own fault all the same.
Anyway the demo was terrific so gonna buy a copy now :D
PS. Is there any way to have the game remember your initials so you don't have to enter them at the end of every race?