I'm not a dog expert but have picked up an awful lot since rescuing my first dog in 2013.
We have a gorgeous rescue collie cross, Tilley (who even has her own website, see
http://woofy.woollypigs.com/2016/09/three-is-the-magic-number/). We wouldn't be without her. She was abandoned before she was six months old on a busy road in Leitrim, Ireland, with her sibling. They were thankfully rescued, ended up at Darlington Dogs Trust and we were lucky enough to be "chosen" by her. (We'd gone for a little look, and ended up with a
hyper, skinny, shit-covered ball of fur... who blossomed into a completely wonderful friend.)
She's affectionate, very intelligent and a proper character. She's chilling out more and more as she gets older. But she is a proper diva at times and is very high-energy. As you've mentioned, I'm not sure a border collie would be right for you, given your circumstances.
I strongly recommend, as mrcharly suggested, checking out your local rescue centres. Dogs Trust figures for 2014-15 showed that one unwanted dog was put to sleep every two hours
by council pounds in the UK, and over 100,000 were abandoned that year. For that reason, and having
fostered unwanted dogs and found them new homes, we would never contemplate buying a puppy from a breeder. YMMV.
You're right that a dog is whatever you put into it. If you're concerned about getting a "damaged" dog from a rescue, don't be. They have plenty of puppies and young dogs who would provide you with a blank canvas to work with. Many provide training (positive reinforcement is the type to go for) as part of the package and rescue back-up in case you need advice or have problems.
I would keep an open mind about suitable breeds. Rescue centre staff will get to know their dogs very well, and you might find that a Heinz 57 is your perfect mutt. Crossbreeds are cheaper to insure and tend to be healthier and live longer than pedigrees, too. Breeds that are traditionally good with kids are lurchers/greyhounds (they are actually very lazy, despite their speed, and like nothing better than a comfy sofa), bull terriers as Ruthie suggested (known as "nanny dogs") and labradors.
But, the most gentle and chilled out dogs I've ever met have been crossbreeds (with the exception of Wowbagger's Morphy who is a pedigree Red Setter). We fostered a gentle giant,
Quinn, who had been tied to railings in a back street in Bradford and dumped. He was the most affectionate, gentle creature despite his dreadful treatment. He was probably collie cross red fox labrador.
Ruby, a rescue puppy from the snowy streets of Romania, was equally chilled out, loved to sleep, and became a perfect family pet. He was a Belgian Shepherd Cross. It really depends on the individual dog, and - of course - what you are prepared to put into the relationship with your four-legged friend.
As well as the Dogs Trust I'd really recommend
Jerry Green Dog Rescue,
Babworth Animal Rescue Kennels (BARK - they have loads of gorgeous little crossbreeds), and
Many Tears in Wales.
When it comes to leaving dogs alone, the rule of thumb recommended by positive reinforcement trainers is no more than 4 hours at a time, which is built up gradually to avoid causing separation anxiety. Many dogs are left for longer than this with no problems, but the majority are just really miserable. They are sociable creatures and can really, really miss their people. Tilley started off with real separation anxiety - she'd whine and cry if we left her alone - so we had to follow a careful training plan, getting her used to her crate and gradually building up her time alone. Three years on, we can now leave her for just over four hours, loose in the house. She's absolutely fine, and actually seeks out her open crate and prefers to sleep in there while we're out. Puppies shouldn't be left for too long at first. (A former schoolmate of mine has just bought a tiny beagle puppy for £800 and expects to leave it in its crate for 8 hours solid while she's at work. You can imagine how I feel about that.
)
Something you could do in the meantime to double check whether having a dog is for you is volunteer with the
Cinnamon Trust. It's a charity which finds volunteer dog walkers/fosterers for the pets of elderly and/or terminally ill people.
Finally, take a look at these beauties just to give you an idea of what is out there. All abandoned and in need of a home. Please adopt, don't shop.
http://www.manytearsrescue.org/display_mtar_dog.php?id=17339 http://www.jerrygreendogs.org.uk/RehomeADog/ShowDog/Blidworth/2016-04-18/Little%20Lucyhttp://www.jerrygreendogs.org.uk/RehomeADog/ShowDog/Broughton/2016-09-21/Piphttps://www.dogstrust.org.uk/rehoming/dogs/dog/filters/~~~0~~n~/1158147/ebonyhttp://www.barkonline.co.uk/adopt-a-dog%20/small-dogs/dingo