Anglo-Saxon Britain had a number of sources for salt outside of the coastal regions. Bede mentions Droitwich as having salt springs, and the area was used as far back as the Iron age, as well as by the Romans. Recent tests show that it is about 4 times saltier than seawater, which makes it very economical in contrast to coastal salt deposits, as it requires less material to refine the salt. The other main locations are the wiches in Cheshire, whose brine-water is about 1/5th weaker than Droitwich, but twice as potent as sea-water. There's a few more places that engage in it but at much smaller levels - Lyme, and various places in Worcester outside of Droitwich. An awful lot of salt was used not just in preservation, but in butter and cheese-making. The Anglo-Saxons ate a lot of meat, (mostly salted pork, but beef, lamb, and chicken) and also fish, all which could and were salted.

Who brings the salt to market? How is it transported?

Both the Crown and the Church got involved with the development of existing salt production, so it would be heavily supported. A Salter would take the salt from the centres off to the outlying areas, and would have to pay a number of tolls which varied on the amount of salt he was taking - 1 penny a cart if you were from the same hundred (area), 4 pence for a cart drawn by 4 oxen, 2p for a horse load etc.,

Would it be cheaper to buy foodstuffs that are already salted?

That's hard to say due to the lack of sources. Regia has a generalised cost list for foodstuffs and farm animals, but this doesn't get you a comparison of costs. Debby Banham's work is probably your best bet at finding out more on that but she's pricey.

You would have to have been pretty wealthy to afford meat. The average peasant wouldn't have eaten meat once in a blue moon. In fact, in the Middle Ages, cheese was referred to as the "white meat" which is funny considering that we sometimes call pork "the other white meat." Anyway, for a lot of cheese production, you would still need salt. In England, salt production had become an industry introduced by the Romans. It was largely located around Cheshire. Salt was a major commodity to the Romans. They even used it to pay their troops. Our world salary comes from the Roman word for salt. So, the thing is that we have the idea that there wasn't a large amount of trade going on during the Middle Ages, and this is far from the truth. The Middle Ages saw the rise of the merchant class. Good traveled throughout the kingdom by cart and waterway. You might not have a merchant carrying salt in your own little hamlet, but a nearby large town or city might. So, you in turn would travel to them. And remember that there were market days, when merchants would come to towns and sell their wares. Salt and other spices would be among them. Of course, the rich would have much greater access to all of these things, but salt was and is a necessity of life. I highly recommend the book "Salt" by Mark Kurlansky. There is also a good website here that has a lot of information on the history of salt: http://www.saltassociation.co.uk/education/salt-history/ancient-times/