The new Makita 18v with Lion batteries are very good .But check that your inverter has enough jam to charge the batteries , otherwise go 12 volt and rig up a direct connection to your vehicle battery .Milwaukee 12 volt drills are very good .
My advice would be to avoid Dewalt [ if they are available in UK ] and Black and Decker .
What about taking a cheap generator ?
Blessed are the cracked, for they let in the light. - Spike Milligan
"When you come to a fork in the road ,take it ! When you come to a spoon in the road ,take that also ."