I have just returned from a couple of weeks in the Polzeath area of North Cornwall.
I go to this area every year, as a fried had a house there, but until now I haven't had much luck with the SIB. 2 years ago I paid to stay on a pontoon at Rock, this was incredibly expensive, the pontoon only had water for about half the tide and the commercial users of the pontoon kept moving my boat. The next year I stopped at the dingy park, this is more reasonable, but it has very soft sand at the bottom of the slipway, which causes the launch wheels to bog down badly.
This year I had a new plan, I kept the boat at the house and moved it around on the roof of the car. I've found two good places to launch - Rock beach near the sailing club and Port Gaverne. The sailing club slipway at Rock goes down onto hard sand with a few small bits of slate. Its hard enough to drive on with a 2wd car and launching wheels don't sink!
Here is the boat at Rock:
Port Gaverne required a £25 annual membership, which is pretty reasonable, even if you are just launching for a week. The beach here is similar: hard sand, which you may drive on with your £25 membership.
The drawback at both launch sites is parking. If you get there early enough there is free on road parking at rock and 6 or so spots at Gaverne. After about 9am, you are looking at a car park at rock, which in the school holidays is full by 11am. At Gaverne, you can park out of the village, but this is a 10 minute walk up a steep hill!
I mainly launched at Gaverne, which is just round the corner from Port Isaac.
Fishing wise I did best out of rock, one day having about 10 bass around Trevose head
Best bass of the week however came from near Port isaac.