I think the park in pwllheli you mean is Hafan y Mor which is now run by havan holidays ,i stayed there in when it was Butlin's Starcoast Pwllheli,in the mid 90's and thought it was good,also stayed in havan Kiln Park which is smaller and probarly more suited to kids in the 3 to 13 age group, as i both of these visits were over 10 year ago so not sure what they would be like now,but here is the link. [broken link removed]