Just catching up on this thread. Glad your dog's OK, Loafer.
Our miniature schnauzer was set upon by two boxers on the loose in our local park, with their owner standing by in the distance holding on to two other dogs and doing nothing to help while my partner and her friend fought to keep the two off. Eventually my partner was able to pick up our dog who was bleeding profusely from a massive wound on her side. Fortunately is was a weekday and our local vet was only a couple of miles away. It was touch and go but after an operation and a few weeks recovery she was physically recovered but was clearly now afraid of open spaces and other dogs.
We reported the incident and put notices up around the park asking if anyone knew the owner. We quickly discovered who he was (he owned a local hairdressing salon) and also discovered that the Dangerous Dogs Act only covers dog-on-human attacks. The dog owning policeman who visited us, who was very sympathetic, said that if the dogs had bitten my partner or her friend they they would have been able to 'get him' under the Act. As it was they couldn't do anything except give him a stern warning.
We had pet insurance, which paid out, and we could have taken the guy to the small claims caught, but decided it was just too much hassle. The only upside to this was that as word spread around the local dog owning community a number of people started to stop going to the hairdressing salon, apparently the owner already had a bad reputation in regard to how he controlled (or not) his dogs. At one point the guy sent a 'friend' round to us complain that we had ruined his reputation, and threatening to take us to court!. It was all bluster, of course, and nothing happened.