especially security! That’s one thing I’ve not considered.
There’s possibly a few other things you need to (or could) consider, too. But, let’s not make it too complicated at the moment. Not least, as most of it is little different to going to going touring and riding a motorcycle in Scotland or indeed, Norfolk.
Start with the simplest things:
A. Do you have a valid passport and does its validity extend six months beyond your anticipated return date?
B. When (time and date) do you plan to leave your front door and when do you anticipate returning to the same front door, time and date.
C. Where and when (location, time, date) do you antiparticle arriving on the Continent? Likewise your departure from the mainland on your return.
If the answer to A is yes, go straight to B and C. If it’s no, go straight to the passport application / renewal website.
The answers to B and C, will (by and large) dictate where it’s possible for you to get to on your jaunt and (maybe) ‘stuff’ to see and do along the way. The answers might even give you a clue as to the likely weather. The latter will become much clearer as you approach the departure date and clearer still each day thereafter.
PS Battlefields are all fine and dandy, depending on the answers to B and C, too. However, despite their size, they are not littered around everywhere. For example, it is 270 miles (direct) from Cherbourg to say, Peronne, in the centre of the Somme battlefields of WW1. That’ll maybe take you most of the day. It’s the same coming back. That is, near enough the same distance as Southampton to York.
Likewise, it Is 340 miles from Cherbourg to the ‘Must do’ Menin Gate at Ypres, on the Belgium / France border. That is the same distance as Southampton to Carlisle.
Told you, France and mainland Europe is a big place.