Hello All - I have recently taken early retirement and would like to own a dog now for the first time ever. Complete beginner so will need lots of help!

I have looked at several breeds and have set my heart on a Cavalier King Charles. I would like to get a rescue rather than go to a breeder, if possible. I have looked at various sites. How best would I go about giving a forever home to a dog, preferably female and preferably not too old so that I would have quite some time with her? I live in Hertfordshire but can travel a reasonable distance. All advice welcome.

Many thanks.