There's been mention of a three year partnership with Eastern. Price and reliability will be key - not previuosly strong points for Eastern. If they get this right DUB and BHD look like no-brainers, LCY still looks brave in competiton with the train (but could offer good onward connection opportunities), CWL is a transfer of an existing service and IOM looks like a summer fill in.
SOU is a surprise, especially if it is twice daily as suggested above. Has SOU ever been served from MME?