If it was possibly enforceable (which it isn't of course) I'd make it illegal for anyone to keep a large dog in a small flat. It's just plain cruel. The welfare of any dog kept in those conditions is going to be compromised even if they are being walked twice a day.

There is a lovely green space round the back of the flats on the London Road and I often cut through there because it's becoming a bit of a haven for wildlife. I even saw wild chives growing there last year until the council mowed over them. Just lately however, I've noticed it being used as an exercise and toilet area for a couple of frankly quite scary looking dogs. I like dogs but it's made me feel uneasy about walking through there sometimes. The owners really don't look very approachable and I doubt they'd take kindly to keeping their dogs on a lead.
I know community support officers are getting a lot of criticism in the press at the moment but this is exactly the type of behaviour they could be policing.