When we visit our son, DIL and grandson for a week, we take the dog with us. It's a simple process as we travel by ferry.
With Brexit we were originally advised in 2021 that Bob would need an EU passport to travel, but thankfully that plan was scraped (after we got him a passport) We do carry his vet book and chip number as we were checked on one occasion due to people smuggling puppies over the sea.
Bob is used to long journeys having started his life in South Africa in 2010, moving to Dubai with us in 2015 and onto the UK in 2020. Him and the cat didn't need crate training they took to it naturally.
He has no problem going in a crate on a plane, at home or at our sons house, but the second you near the kennels on board the ferry he starts to run on the spot on the slippery surface as he tries to dig his feet in.
He doesn't get travel sick in the car and it's almost 3 hours to the docks, before we even get on board, followed by another 7 hours on the sea.
He greeted us like this in the morning.