Jon,
I had a Plymouth Pilot 18, for a couple of years.
Extremely economical to run but very slow.
Strangely, it was as steady as a rock motoring through almost any seas (I was out in some very large waves in it) but it used to roll very badly at anchor.
With the inboard engine the fishing space was also reduced quite considerably, although we did use the engine housing as our "cutting tray", but it still limited the deck space a lot.
If you intend fishing inshore (or better still inside the harbour) they are solid heavy boats. Just about trailable, although because they are a displacement hull, there are few straight lines for rollers so they can be a bit of a bugger to get onto the trailer if there is any wind or swell.
Most important, if you intend keeping it on a mooring, check the seals on the fore and aft decks. Put your head inside and look for daylight. Often the seals look ok, but leak water and you will find yourself having to bail her out every week of so during the wet seasons.
Any specific questions, just ask.
Graham