Stuart,
PVC Dollies are all right in the short run (2-3 years) for the cost. Scroung around for wheels/tires (wheelbarrow/ lawn tractor front wheels) and axel (grounding rod). You have to treat them gently (not real strong), keep them out of the sun when not in use (UV deterioration), and like to be pulled better than pushed (even with big tires). How do I know, I made one and am using it for now until I get a trailer and or aluminum dolly. I think you will be better off with a Seitech or Spootride. The following are some PVC ideas and the addresses for the aluminum ones:
I have two homemade dollys. One has lasted me 25 yrs. I used the rear wheels from an adult tricycle. The dolly fits into the daggerboard well. It balances nicely and there's next to no rolling resistance. You can push the boat and gear for as far as you care to walk. In my opinion it's "heads & tails" better than any commercially available unit. I would not describe it as cheap. The main cost being the reconditioning of the wheels at the local bicycle shop. I'm about 75' above the beach, so I go up & down hill with it all the time.