I've been reading the forum for a few weeks but being an exiled geordie (20 years in London) I haven't posted before (anyone want to know about fishing the kent coast or Bewl water for Trout I'm your man!).
Circle hooks I've experimented with a lot. To catch, the fish has to swim away with the bait in its mouth, ideally pulling across the corner of it's mouth so the hook catches in the scissors. This makes them ideal for flatties but I'm not convinced for round fish, especially if they are being a bit finicky ?
If there are a lot of fish about and your using a multi hook rig, they work well, and I can see the benefits in kelp/snaggy ground because they won't snag up anywhere near as easily as a J hook.
There are some "semi" circle hooks around which are a compromise and may give you more confidence, but you may as well use a normal hook if your going to do this.
They key to using circle hooks is NOT striking. If you strike all you'll do is pull the hook out of it's mouth. To set the hook you have to wind in and tighten into the fish, allowing the circle to find its hold.
They are unbeatable for livebaiting!