I use blue water pipe that was left over from projects or builders' waste. It's ok, but not brilliant. The smaller diameter stuff isn't that stable and even in the larger diameter's it's a bit wobbly for large beds.
Netting, fleece and suchlike I've bought from
these people or
these, who seem to be ok and may in fact be the same business. Larger sizes seem to work out much cheaper for some items, so it's handy if you can find someone to split the purchase with. It's often recommended that you get the heavier weight of fleece as it's a bit more robust and keeps the heat in better.
James