Yeah, at most they might drag up a token force from the Pacific Fleet or other areas, but....TBH, I'm not sure even the British would risk operating in the Adriatic Sea, even with French support. Not against both the Habsburgs and the Italians, not without overwhelming numerical superiority. And I don't see that happening without Britain having to transfer ships from home commands, which would be even more unthinkable, what with the threat of the High Seas Fleet and the First Scouting Group.
That said, ironically, they do control the entrances to the Med, so really, it's easy for them to close it off.