Before cooking the belly you need to slash the skin with a stanley knife. Please don't bother even attempting this with a regular kitchen knife. It just won't work. Working from one end of the meat you need to make cuts through the skin and fat every 2 cm. Rub course salt into the cuts.
Cook the belly for 20-30 minutes at an incredibly high temperature (240 degrees). This crisps up the crackling. Turn the temperature down to 180 degrees, and cook for a couple of hours. What you have, at the end of cooking, is crunchy, golden, salty crackling and soft, juicy, sweet and tender meat. It is heavenly, but terribly rich. You won't need much.
I served mine with potato, carrot and spring onion mash, peas and apple sauce. The apple sauce balanced the fatty richness of the meal perfectly. The leftovers make the most divine sandwiches, or alternatively, stir-fry chunks of cooked pork in a satay sauce (peanut butter, soy sauce, chillies, garlic & a little brown sugar) and enjoy with egg fried rice.
So, pork belly, for £4 you can have sumptuous roast dinners, some super tasty sandwiches and a 10 minute stir-fry supper. Bargain. And just think, if pork belly is £4 in M&S, imagine how cheap it will be in ASDA! And in Lidl, well, they'd probably pay you to take it away.