G'day Tony,
My advice is to hit up a reputable local mower shop. If you're looking to get started, you'll need engineering support along your way. A good rapport from day one could be priceless.
If you're set on Bunnings, Masport isn't a bad bet. I can't speak for their longevity in a commercial environment. But still check out the mower shop down the road. You might be surprised.
