Many years ago I took the Plymouth - St Malo ferry with a tandem, which leaves you only a couple of TER journeys away from Nantes.
Every website will discourage you from taking tandems on trains. It seems like Cross Country have free bike spaces, but they say no tandems. In my experience it's always a risk but it tends to work out if you have no shame. In the French TERs I already hung our tandem upright near the toilet, just made sure it was safe and not blocking anyone's way. In the one or two events we didn't manage to board we were lucky to be able to wait for the next train and try again. Rules are applied by people, and some people are nice.
I know nobody wants to plan and buy tickets for a long trip knowing that it can fail at any point, and it may well be that rules are stricter now than 10 years ago. But my hunch is that if you find a way to get the bike to Plymouth you'll be fine.
this. the biggie is trains like the gwr trains with insane designs for bike racks but, otherwise, if it will fit then there’s likely to be a nice person to let it on
Many years ago I took the Plymouth - St Malo ferry with a tandem, which leaves you only a couple of TER journeys away from Nantes.
Every website will discourage you from taking tandems on trains. It seems like Cross Country have free bike spaces, but they say no tandems. In my experience it's always a risk but it tends to work out if you have no shame. In the French TERs I already hung our tandem upright near the toilet, just made sure it was safe and not blocking anyone's way. In the one or two events we didn't manage to board we were lucky to be able to wait for the next train and try again. Rules are applied by people, and some people are nice.
I know nobody wants to plan and buy tickets for a long trip knowing that it can fail at any point, and it may well be that rules are stricter now than 10 years ago. But my hunch is that if you find a way to get the bike to Plymouth you'll be fine.