Hi, just to update,
I've gone as far as factory resetting & clean reinstall of the entire laptop and it has made no difference at all. This game remains unplayable.
As it used to play perfectly on this laptop and I've been in touch with the laptop manufacturers to confirm there are no system updates I've missed (doesn't matter now anyway as I've re-downloaded and reinstalled the entire system), I can only conclude that it is the game not the system and one of the updates has buggered it which is disappointing.
Many thanks for the suggestions nonetheless.