You could take the Condor Ferry from Portsmouth (slow) or Poole (fast) to Guernsey and try Fauquets Valley Camping
Camping in Guernsey Pool and cafe. Toilets spotless.
You can either have a marked spot with power supply or join us in the Outback field where it's camp where you like but much more peaceful.
Lots to do on the island including many miles of beaches. Eating out is very cheap compared to UK as taxes are lower. Local bike hire will deliver to the camp site for you if you want to not use the car. Bus stops are 20 mins walk, so the only down side.
Enjoy, we do!
Adam