Thank you all for your help. It's been sorted. The problem was with other users still logged in.

Thanks again

Thanks guys for your replies.

How about the point 4 on "Unable to delete relationship FK..." Do I have to delete the relationship and then change it? But it...

Yes sorry. The error is:

1: When I click after change to Save, the Save box shows "The following tables will be saved to your database. Do you...