"Or two cocker spaniels. They've always seemed a more calm dog compared to springers and border collies."
If that's been your experience with Cockers you've met the exception that proves the rule; I've kept Spaniels all my life and the Cockers are the 'fizziest' of all the breeds, as a general rule.
Reading through this thread I reckon the best choice for the situation you describe would definitely be the Border Terrier. And if you mean for the dog(s) to be alone for the periods you mention you need to bear in mind that you can't leave
any breed alone
at all for a considerable time after you first acquire them; they need to be socialised, find their place in your pack and to have matured enough to remain psychologically sound and secure before you leave them alone in either house or garden for any length of time. That maturing soundly is what makes or breaks a dog, and it doesn't happen quickly, it can take many months and sometimes more.
I hear what many have said about leaving their dogs for longish periods, but in my experience this rarely leads to a well balanced animal and I have never done it; the longest I've ever felt comfortable with is a couple of hours maximum, and that rarely.
Just my thoughts, I don't mean to be preachy or call anybody else wrong