In reply to Hans:
My first few long distance rides were done with a bag of lightweight clothes and a credit car. that worked very well. Managed 255 miles in 2 1/2 days and a total of 16 hours cycling. Booking B&B's ahead proved to be not such a good idea so I then went on to lightweight touring equipment as follows
1. Event bivi bag
2. Tarp and string for a rain shelter.
3. Feather sleeping bag.
4. 3/4 length carry mat
5. credit card.
The kit has seen me from Bristol to Folkstone around the coast via Lands End so far (5-600 miles).
That all fits in one pannier bag, so can be supplemented with some food and water if it doesn't look likely that I'll be able to buy a meal in a pub (never happened so far!).
There are of course people of would regard this as cheating!