Hi these compared to leaving a championship when for example I'm in div 4 england I decided to go to France when I go to France I would go up to D3 French or ???

Hi if you choose to leave your championship you will be excluded at the update of the new season, then you will have to register in the championship where you want to go and start with the lowest division.
For example if there are only 3 divisions you will be in a group in D3, if there are 8 divisions you will be in a group in D8