I'm not from the UK, but here's what I found, from:
http://www.outlawcook.com/Page0117.html
In the country, and I don't mean the garden counties around London, but in the West Country, in Somerset, Devon, and Hereford -- in fact all over rural England -- the pubs serve one of the finest lunches ever devised, incredibly simple, rustic and plain, yet a meal that can be memorable given the right conditions. Called a "ploughman's lunch," it consists of a cut of Cheddar, a home-baked bread roll, pickled onions and a pint of beer ..... Adrian Bailey
That is, if you're lucky in your choice of a pub. The ploughman's lunch is easily the most universal pub snack but it is often a travesty of its namesake: a slab of factory Cheddar, a piece of "French" bread, and some over-pickled onions. When ploughmen actually ate such a lunch -- then simply called "bait" -- the cheese would have been equal in size to the bread and both would have come from the farm whose fields were being ploughed. And the onion would have been both fresh and raw and eaten like an apple.
