http://www.biobees.com/forum/I think the guy who set up this forum is in Devon and he is really nice and helpful. When I had bees (before they succumbed to the spray one spring) I got a lot of knowledge from it, and they will help out with hives other than top bar
I know it goes against everything everyone says, but if you can get a second hand hive or bait hive you have a much better chance of attracting a swarm, the other thing which is quite good is lemon grass oil, which seems just like queen bee pheremone.
Bees hate new hives by the way, and even if you install a swarm they will often decamp, so if you are making new then do plenty of rubbing round it with beeswax and propolis to make it smell bee friendly - a bit of comb with honey in it is a good attractant as well
I was on the beekeepers swarm list for a couple of years but never got a call, even though I was a member withoug any bees at the time. Once I got my own swarm arrive I was up to 8 hives in quite a short time, and the produced me some honey as well.