Great question Karen, I know it was very daunting when I did it with Diva, Pet passport is obviously a must, I am sure there are more experienced people than me to guide you one that one, I have only done it with Diva. For my trip I wasn't very organised it just was decided to go for it a week before hand, Peter and I went via the Channel tunnel booked the day before, we stayed in Ibis hotels throughout Europe we took a book of Ibis hotels with us and once we were on the road and sort of knew how far we would get each day we would pick one phone and book in to it!!! All let Diva into the rooms with us and restaurants, so it was very easy. Not good dog walking though usually a patch of grass out the back but with a hot bitch I didn't fancy letting her off the lead anyway!!!!! All the ferries bar the one coming back into the UK, (we came back on the ferry as the tunnel was closed due to an incident) anyway all bar the UK one let Diva up on Deck, into anywhere except the duty free, odd she was allowed in the restaurants and coffee shops but not the duty free places. It was very easy but we did go in winter so wasn't very busy, not sure if it makes a difference.
I will look forward to reading every ones experiences on this subject as may go to Europe again next year. Sue Woods often goes so no doubt she will have some good suggestions too.