Martin,
I'm affraid I haven't produced a watt, the electical side of wind turbines is definitely my weak point. I have thought about using the same cycle hub as I used in the photo to build a generator, but I haven't done anything about it yet. So all the power I have produced so far is spinning the weights in the photo. That is not a fair test because all the energy goes into a flywheel effect and smoothes out the turning of the blades. But I am sure that my blades would power your generator.
I am glad that you are in the UK (I am in Norfolk)because it seems we are about the only country that uses PVC in guttering. For small turbines I see no need to go to the expense of soil pipe. I have used the Deep Flow brand also; this type of guttering is the same as standard guttering, but with a higher side (more a U shape). When this is cut down the middle the two blanks are asymetrical, and they look like the top of and aerofoil. Being wider I was able to make a longer blade (.75mm). I made two blades and put them on in place of the ones in the photo. Like everyone here says: as soon as you test something the wind drops. So it was like that for days. But then late one day the wind picked up and I went to bed with the wind rising strongly. The next day I found my turbine off the mast with a broken blade (it had struck the mast). I then made a .5mm bladed three blade rotor. But it doesn't run smoothly, so I think the standard guttering is best, and it is a lot cheeper. You can buy 170mm diameter industrial PVC guttering, but this is very expensive and hard to find.
The rotor I have on the mast now is almost the full Monty except for one thing - no alternator. But it has a generator fixing mount, a yaw mount, and it furls. All the parts can be sourced from B&Q (I still shop there, even though they are misselling the Windsave tubine). But all this, of course, is academic if I have not produced any electricity yet, but being on grid, even though I live in a rural setting, it is just a hobby with me.
PVC guttering is cheap, it won't cost you much to experiment with it, so my advice is to have a go at it. If you do, let me know and I will pass on any tips on cutting and such, that I have learnt - generally the hard way.