Welcome, Pete! I know the feeling! The first run at Piratez can be very challenging, and you can feel lost at every turn.
Shippings: Many of them will fly faster than you. The trick is learning how to catch them when they land. Many enemy missions involve some time on the ground. If you can tail them with the Bonaventura, until they land you are in good shape. If not, try to anticipate where they are going and patrol with the Bonny in those areas. If there was a recent mission in South Africa, chances are this next one might go there too.
As soon as you can afford it, hire some Pigeons to help you cover where there is enemy activity. You can use the Charts to see enemy activity in both regions and countries. With 2 or 3 pigeons, you can cover alot of this, then send the Bonny out to scout, when a contact does appear.
The next tier of surveillance, is Spy Zeppelins. Once you are able to construct them, its not difficult to put almost every land mass under surveillance.
As far as the Hunter-Killer for a fast interceptor, you can hire out the Shark Jetbike. It has been my scout for the entirety of my current campaign as soon as I could afford one. I have pretty much stuck to only going after landed vessels in the first year, and it has served me well.