UK tunnels can be used by vehicles carrying removable cylinders provided the gas is turned off at the cylinder valve, though there may be a limit on the total amount of gas carried, normally well in excess of the amount on a caravan or motorhome. Rules vary on the continent and you are advised to contact the Club’s Travel Services for specific advice before travel.
Roll-on roll-off ferries have similar rules, though there are some variations both in the UK and continental Europe so check with your ferry operator. Generally, the number of cylinders you are carrying must be declared to the ferry company and to ship’s officers, and there must be no more than three (two in the case of some operators). All must be secured against movement and shut off at the cylinder valve during the voyage. Eurotunnel currently permits a maximum of 50kg of gas to be carried with the portable cylinders and 47Kg for a fixed installation both turned off and isolated.
If you have a motorhome with a fixed LPG tank be aware that some tunnels and ferries may limit the amount of gas that can be carried, so check with the operator first.