Dammit, I had to buy stuff...

Work on the hen house is proceeding well. Having gathered most of the materials from various places, and all for free, it came as a bit of a shock to actually have to pay for something!
But the scavenged guttering, and drainpipe, needed fixing in place and no fixings could be found so I decided that I would go and buy the few bits I needed.
3 gutter clips, 1 pipe clip, 3 gutter end stops, and an end piece to join the gutter to the pipe. About £13. But the gutter needs to be trimmed... Add a hacksaw for £4. Tools are always a longer term investment, so I'm not counting that cost against the hen house build costs. I'd already included the gutter fixings in my original house cost tally of roughly £30.

That's the hen house, all painted and ready for the guttering. The pallet at the side is the start of the run, and will be turned the other way up, trimmed and attached to the house before being covered with wire mesh. More on the mesh in a moment.

Guttering in place, and drinking trough working! One of the few times I actually wish it would rain so the system can be tested properly. I've poured a watering can full of water over the roof and it works! The water runs into the gutter, down the pipe, and catches in the trough at the bottom. There was a slight leak/overspill at one end but a piece of pond liner stopped that, and protects the hinges on the nest box too.
Today I've used a length of roofing baton to make a perch inside the house, and some offcuts to make a ramp from a piece of scaffolding board for the front. 
So, the hen house is finished and ready for occupation, except there's no run....
Wilkinson's have had a sale.
Wire mesh: 25mm netting; 600mm high, 10m long. £1.25 per roll. 5 rolls (all they had on the shelf) Thank you very much.
Now to make the frame for the run, add the wire netting, maybe look at some of the stronger stuff for the bottom layer, and it'll be good to go!
So far, with the netting, it's looking like £35 for materials. But I'm going to need some hinges and a bolt/catch for a door into the run. It'll be more like £40 all in, I think.