I have an 8yo PRT bitch and last year we got an 8mo border terrier cross from rescue.
I'd agree with absolutely everything everyone has said about PRT/JRTs! :o
Very independent, very willful and determined, astonishingly affectionate with people, dodgy with (some) other dogs. She's got more grumpy as she gets older (much like me, in fact).
Easy to train, but you have to put in the hours, and when she was younger she had more energy than any other dog I have ever met (and we used to have a working border collie!!). She can still outrun every single dog we know.
She was never a chewer, and has no prey drive, she's also not overly barky.
She's fine to be left for a few hours, it's one of the reasons we chose the breed.
The border terrier cross, who is now about 16mo, is an absolute dream of a dog and tbh if I was looking for another dog I'd be very keen to get another bt - she is unbelievable affectionate with everyone (dogs, adults, children), cheery, clever, easy to train, happy to go out and about but will also flop about dozing if we're having a quiet day. Really really wonderful dog. She does chew a lot, though, which I'm hoping she will grow out of, but is happy to chew on her toys and antlers etc rather than our shoes/furniture.
I would totally recommend border terriers!