If you have a 4ft you might as well go with a beardie, perfect size for a full grown one. Rankins are a bit smaller. I don't have much experience with rankins but I know beardies make a great family pet and a pleasure to handle as long as they're handled often to keep them used to it
Always keep them alone, never ever ever house together. There's not always physical aggression but there's always domination resulting in one not getting th good basking spots, being forced to hide away all the time, not get food etc. Keep them alone
If you're after rehoming go to the classified section on here, there's either the lizard section where people sell their unwanted ones (for whatever reason they don't want them, usually good reasons!) and there's the rehoming section for rescue animals and while I've only seen a couple beardies on there you might find one.
Lizard Classifieds - Reptile Forums
Rehoming Classifieds - Reptile Forums
If you're on Facebook I highly recommend joining Bearded Dragons UK.
The admins are all lovely people and eager to help, helped me a hell of a lot when I first started