head off down yer local dump, most now have compost for free (Blairgowrie does now as well). FYI - it ain't the best in the world but it is free. Most of it comes from garden waste & cardboard, the latter of which relies on folks taking all of the sellotape etc. off of boxes - which having in the past watch what gets dumped ain't always the case. So worse case scenario expect to get bits of plastic & other "shite" which you'll have to pick out, that aside its free so go get collecting.
Oh & B'gowrie never put a limit on the number of bags, just as well...its all gone for the mo thou...might be due to me!!