Wow! Thanks for all the suggestions and advice. I like the idea of the bottle path - means I've got a good excuse to drink lots of wine so I can recycle the bottles
I'm not so sure about the powered fan system as it's a long way from an electricity source but if I ever get a small solar panel I'll definitely give it a go.
I'll follow some of these up and let you know how it works out.
I thought it was cold enough here in Wales but I think Durness beats our record! I'm surprised you can grow much up there. Mind you, I recall seeing a sign for a hydroponic nursery just beyond Ullapool last time I was there.
Richard
Richard