We normally use Kerr and Ball canning jars. They come with lids and rings to retain the lids. The lids have a rubber seal on the lip that stay in contact with the rim of the jars, AND (most importantly), they have a slight convex curve in the center that "pops" down after processing to show that you have a proper vacuum seal. After removing the processed jars from the water bath canner, I place them on wire racks to cool, and eventually the lids all "pop" down. I don't know where you can get the best deal in the UK, but here in the states, you can often get canning jars in case-lots at hardware store and big garden stores like Agway. You should plan your purchases to avoid having to buy both sizes of lids and rings. I like wide-mouth canning jars because it's easy to load the food in. You can find wide-mouth canning jars in quart, pint, and smaller sizes. The next canning season, you'll only have to buy and store wide-mouth lids. The jars and rings last for years - only the lid inserts are disposable. If you go to a place with canning supplies, pick up a box of wide-mouth plastic lids, too. Once you have opened a jar of some food, toss the metal lid, put the ring someplace for storage, and re-cover the jar with a plastic lid before you stick it in the refrigerator. It's a minor convenience, but I find that the plastic lids do a good job and are less likely to stick to the jar if there is some kind of juice on the threads of the jar.