London to Mont St. Michel in France

The best way would be to fly to somewhere in the country you want to go to rather than London, but I assume that particular horse has bolted.

It looks like EasyJet fly from LGW on Mondays and Fridays. That's already inconvenient meaning an airport change and some dates the flights are too early for you to catch anyway. There will no doubt be flights to Nantes as well but there may be the same issue with changing airports, timings and maybe days when the flights don't run.

Brittany Ferries run an overnight service from Portsmouth to St Malo. That obviously means getting to Portsmouth and then having a second overnight journey after the flight and not getting there until day 2.

I'm sure a flight to Paris would have been a whole lot easier.

Keolis run a bus from St Malo to Mont St Michel daily at 0925, journey time 1 hour.

The easiest way from London direct to Portsmouth Ferryport is on the National Express Bus.

So the ferry route is not a bad one, avoids changing stations across Paris as you would by train, and uses time efficiently by being overnight.

Usually the ferry leaves at 2015 (8.15pm) and arrives at 0815 next morning.

The other way the ferry takes 2:15 hours less (by day) so there is plenty of slack time there.

Thank you for the information!