Great Western Coffee Shop

I'm headed for Weymouth tomorrow - 09:43 train from Melksham and meeting up with a whole bunch of friends.  Plan is for us all to come back late in the day.

Questions

- if one or two members of the group wish to return early (leaving at least three in the core group) do those one or two just have to pay the difference in fares, or do they need new tickets?  Is it OK for the core group of 3 or more to return on the group save, or would they have to pay more or again too?

- if we buy a group save for (say) seven people, can we come back as a group of three and a group of four, or do we need to make a decision when we initially buy?  How does it work if we wish to jiggle around during the day between the groups?

Provided each of the split groups have three or more, then the Groupsave tickets are still valid. When individuals split from the Group, they should pay an excess of the difference between the Groupsave and full fare - unless, of course, the individual has a valid railcard, in which case a conversation with the guard should suffice.