Thanks MaxYablockin that helped a lot.
2 problems, the first is that it moves the game navigation menu (as in the one when you're not in the main menu). To fix this I moved the xpos 0.5 from the navigation section to the "if main_menu:" section and it worked fine.
The second problem is something I need a little help with, for some reason the text isn't centred.
And changing the xpos makes it move larger amounts that would be expected, for example if I set it to xpos 0.4 then it just jumps really far to the left.
I think could do a half fix by working out the point closing to the centre with trial and error but I think that may cause some more problems down the line.