there are many in the North West, but the North West is a big place, assuming you are coming over on the ferry have a look at this place. Poplar Grove Farm Caravan Park , its between Preston and Lancaster, just pop that text into Google ( other search engines are available) and that will take you onto the site and a lot of other ones
Well it's no where near the North west but I know of a trout reservoir here in South Wales that has a very basic little bothy on the banks. I'm not sure about permits etc for the fishing but google is your friend. You have to walk in and walk to get wood if you want a fire but the remoteness is the charm of the place.