sign up to FB groups like Campervan/Caravanning Stopovers. There are 1000s of suggestions for welcoming overnight stays in pub car parks etc. Some have hook ups, showers too. Can use toilets obv.
For the boaters we enjoyed the waterways car parks in Ireland especially on the Shannon. Free facilities (tokens for showers) and free berths for boats. Loads of older men living in old boats all year cruising up and down the Shannon. Saw a couple set off for the pub at 4pm and come back at closing time. Beats a bedsit or even a suburban bungalow.