Ok, here's what you want to do. Go to your local butchers or farmers market with butchers (they usually give free cooked samples), and ask about their sausages. You'll find a sausage that is more meat, less bread-filler, more flavor than what you'd get from the pre-packaged usual dross on the grocery store shelves. Barring that, check out the gourmet-looking sausages on the shelf (they vary from region to region) and try what looks good. M&S usually have a good meat selection, better than your average store, too.
As for the gammon in the shops, you'll want to get the big gammon steaks and put those on your grill - OMG those are so good. If you like ham & eggs, those are the hams to get. ASDA does an 'extra special' version of them and they are delicious.
