Well, it makes the normal sort of 'tick tick tick tick tick' noise when its freewheeling, but this is something that only started last night. I was riding along when I became aware of the noise, I thought it might be a leaf or something stuck in the brakes at first, but I couldn't find anything. I turned it over by the roadside and span the pedals to get the wheel going round, which is when I realised it was coming from the hub.
There is a reflector in the spokes opposite the valve (which I reckon weighs more than the valve) and with that at the three o clock position it does rotate round to the bottom by itself. It just feels a little sluggish compared to before the noise started happening, when I stop pedalling I just seem to slow down quicker than usual.
Its a strange kind of noise, a little like when you rub the top of a wine glass and it makes a ringing tone (but you know, not a ring tone). I'm taking it into a bike shop tonight, I'm just wondering what to expect really, whether it'll be something that can realistically be fixed in an hour or so, or if it's more likely gonna mean leaving it with them for a few days.