My experience is that there are no supermarkets (including Waitrose) that sell decent bacon. You need to go to a butcher that prepares their own or buys direct from a specialist producer, a Farm Shop or a farmer's market.
Try and get bacon that is dry cured, that is the curing process is done by placing the meat in dry salt. Most, possible all, supermarket bacon is cured in brine and the bacon absorbs a lot of water from the brine and then shrinks and produces that nasty white foam when cooked.