I've done the northern coast to Lands End and wild camped nearly all of it. If you are having an evening meal in a pub don't be afraid to ask about camping in the pub garden. Can cost a £5 but well worth it and you might be able to join them for a paid breakfast.
I have done a few coastal paths and find that there is lots of livestock so treating water is not always the preferred option. I often get water at toilets, cafes, pubs even asked at farms.