I would have thought most people train at one, maybe two schools so generally would not have experience of multiple schools so would be hard to recommend their top three. To be honest you probably need to narrow your parameters. Decide on location first, then find nearest training school with a good reputation.
Not sure Ex Military is something I would focus on, there are some good Ex-Military and some not so good Ex-Military, but I do agree with the rest of what Hughes500 says. I would add to his list though that it is important to check the school has well maintained modern helicopters. I would recommend going to a small school with high hour instructors who offer a personal services.