Thanks for all the advice guys, but unfortunately the only way I could get (PC settings) restored was to do a system refresh.
I thought the high contrast on/off might have been it, but unfortunately it was not the problem as activating it on/off results in system wide changes to all screens and the problem I had was just with the PC settings app. Seems something got corrupted and the system refresh put the corrupted files right. Shame system restore could not do the same thing as rolling back a week would have been less of a pain in the backside option and I know that only last week everything was fine.
Overall I am starting to lose confidence in the new Metro front end as it seems to not be robust enough, this is the second major system refresh/reset that I have had to perform in the time that I have owned Windows 8.
The first time none of the Metro apps would open, they just crashed back to the start screen. The underlying desktop environment is fine as it is as reliable as windows 7, however the new start screen environment seems to lack a reset procedure that can be performed easily if something goes wrong.
Carrying out a refresh/reset procedure seems a bit drastic each time and the need to put back programs in the desktop environment is a pain, especially as it is the Metro part that seems to give me the most problems.
I am now hoping that it is a case of 3rd time lucky and that from now on Metro behaves itself. If however this proves not to be the case than I think a downgrade back to Windows 7 will be my course of action, as I didn`t have any problems with this in the 3 years I ran it and I have better things to do with my time than to spend hours putting things back to normal after a Windows 8 fail.