OK managed to fix it from advise from another user (thanks Nottmred88!!) don't know if you want add this to a sticky.
Once you update from Win7 to Win8 you need to delete your setting files
Football Manager FAQ
Then re-verify your cache
Football Manager FAQ
Next time you open the game it'll re-install. All other saves games are OK etc.
To answer your question about 8. You seem to be able to use it similar to 7 if you really want to but there area bit of user friendly things thrown in once you get used to it, but only being using it a couple of nights
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