I use 1 inch wide bag strap stuff from the local haberdashery store, it is sold for 35P a metre. So that is £1.40 for 6 metres.
The bloke did tell what what the proper name for the stuff is but I cant remember, some name like poly webbing, it is rucksack straps stuff. It can stretch slightly if me and both kids get in one hammock [@25-30 stone].