John.
1) Do you still have your UK shotgun certificate?
2) you will already have an EFP (European Fire Arms Pass). It s the same throughout Europe. Little blue fold out document.
3) if 1) above is a 'no' then you will need a British Visitor Visa. Dead easy to get. Look for the form on Cpsa website (link here if it works
https://www.cpsa.co.uk/vsp ).
4) I never ever use the ferry. They can be stroppy and depending on the type of hull (hovercraft etc) the do not like cartridges. Many times we have had them 'removed' in years gone by. The most simplest way to come back and forth is Euro tunnel (not Euro star...they do not allow guns).
5) Eurotunnel....drive car on....you can bright whatever cartridges you want....secured in cartridge magazine of sealed slabs etc.
We used to come back from France full up with Mary Arm .....great wines....and Booze and **** from the duty free. You can pack the kitchen sink when coming by car.....my most preferred way of going trans Europe.
6) loads of hotels. Don't advertise the gun. (Ie don't carry it in...in a slip of course) In a hard case...they look like instruments etc etc... (Well mine doesn't because it has always had England and GBR badges....plus Fiocchi.....plus all the armoury tags over the years....oh....and a big Perazzi sign...... BUT.... Apart from that......it looks like I am from an orchestra ..!
7) I never split it up and leave any in the car....FFS someone might nick my car. Nope I have a lockable wire. It gets chained to a radiator or the bath handles. Easy peasy.
8) let me know if you are doing the Bisley one...it is only 1 hour away.