Leisure batteries like the ones mentioned by Roger are not too bad price wise, and they are designed for deep discharge...ie running flat between charges It may be worth ringing around some local caravan/camping shops.Here is one link I found http://www.countybattery.co.uk/cgi-bin/linkcat.cgi?name=Leisure~and~Camping~Batteries.... nothttp://www.countybattery.co.uk/cgi-b...d~Camping~Batt eries....not as good as a Hawker no doubt but for the use you have in mind more than ample I would think. I am sure with some more searching even better deals are available

Tom

Tom