Might be worth paying the fine just to jolly it out £30 innate, I expect to pay more when I'm out in more normal times.
Take a pack lunch, that half the fine near paid, assuming you get stopped. I'd probably get another 60 quid fine for not having the correct size plate
If I have to go out I will use my bike if possible. If not then it will be the car. The bike is the only thing that helps with my mental stability and well being , if that results in a fine then I am happy to pay. I will use my common sense and refuse to hide in a hole with my tin hat on.
Barmouth is a destination for bikers from the West Midlands we used to see plenty fueling up when we got our fuel for trials riding. Not surprised you got stopped heading in that direction.