I have a special case cavalier -- mentioned before -- that has checked out fine on temperament testing but needs a very special home. It would be possible for him to go to the UK if the relevant homechecks and back-ups can be arranged.
This is a 5 year old male who has basically been an unwanted dog most of his life and lots was expected of him which he didn't know how to deliver because no one taught him. He is as a result, very shy and fearful and has been known to snap in some situations, which seem to have been triggered for some predictable reasons. However a professional evaluation says that he needs mostly a calm environment where he is wanted, time, patience and TLC as well as some cheerful, positive training. He would need an experienced owner who would feel comfortable working with such a dog but I've no doubt the rewards would be enormous and probably would come quickly once he is in the right environment. He needs an adult home or one with teen+ children.
To give a sense of what he is like, though he was quite fearful, he can be held and carried, walked and stroked, and even was fine around a toddler who was running around him -- though he has been known to snap at the child when the child went right up to his face and who was basically left unsupervised with him. Thus he is not an unpredictable nippy dog but one that needs careful and constant supervision when around any children and would be better off away from them as he adjusts to a new life; needs gentleness and attention and fun in his life. I believe he could be managed with other dogs too, but that would need to be discussed. I am told he is a really lovely cavalier, a big fellow who needs a bit of a diet too!
Full backup and advice from pro behaviouralists will be available. Please consider such a challenge carefully -- to be blunt, this isn't a dog to take on because you feel sad for him, but because you feel able for a dog that will not be likely to settle in gratefully but will need a special kind of patience. In this he will be temperamentally quite similar to how many puppy farm cavaliers are, so it is a similar type of challenge with similar rewards. If you feel you could offer this to him, please PM me.