Sounds like a flat battery.The doors etc. dont need a lot of power, but turning the engine does. You can buy a simple multimeter or clip-on tester from Halfords etc, or even easier, one like this (copy and paste url)
http://uk.ebid.net/perl/auction.cgi?mo=auction&auction=23532752&from=googlebase
which just plugs in to the lighter socket.
Local suppliers, tool shops, motor factors etc should stock something similar.
calum, January 2010
