The south end of the island can get a bit shallow around low water springs if crossing from Conway,safer around the north end or use Penmaen swatch,I do know people who have anchored off Llandudno overnight but not something I would do in a small boat.
Perfectly safe if fitted correctly in a cockpit locker or engine space vented outside and the air to be heated taken from the cabin not from the vicinty of the heater because if you get an exhaust leak it will blow it in too cabin.
I have seen some fitted this way.
E08 is flame extinguised,usually through lack of fuel or temp senser faulty,it has 2 goes of trying to start and then comes up with code E10 if still not fired up.