[Arran]

 For long wire antennas, outdoor ones, I have heard of guys using MIG welding wire, it's steel wire, but plated so it will last a few years at least, and it's cheap! Another option is to use disused coax cable from a cable TV install, usually when you move into a house and have a cable hooked up the first thing the cable installer does is disconnect the old lines make a new run of cable, but the old stuff is still there. Connect the antenna lead to the braided wire shield on the outside of the cable. I've also used left over house wire, I had several coils of 14 gauge single strand and strung some of it outside.
Regards
Arran