I know I'm a few months late, but I just wanted to let you know that you can get your guinea pig to the UK without quarantine if you go through another EU country. This is what I did with my rabbit, the UK doesn't have any regulations for taking rodents or rabbits in so long as you're going through another EU country. Amsterdam and France do not have quarantine regulations for rodents, you just need a health certificate so if you go in through Amsterdam and then fly to the UK, you'll avoid the quarantine regulation. Really weird that they do it that way, but there ya go!