Thanks to all for the replies, much appreciated. I ended up blowing this months modelling budget on new fish for my aquarium... so my experimenting will have to wait until next pay-day now.
Electronic grass looks good, but looks expensive, and I'm the kind of modeller who likes to use 'whatevers available' for scenic stuff, rather than buy stuff in. I've tried some artificial furs, but haven't been impressed with my own efforts so far (this is a reflection on my modelling skills rather than the material or anyone elses use of) and I've done the paintbrush thing too. I once bought a brush from the local pound shop and promptly bewildered everyone in work by cutting all the bristles off so I could get on with some modelling once I got home.
While buying my fish today I came across some birds nesting material which came in a big bag for 99p. I reckon if I tease the threads of this stuff in the same direction and dye it light green/yellow, I may have something worth reporting back with. A very quick test tonight looks promising, but not much more than that.
Pete