+1 for the Supercheap bad (in D4D speak - he's been taking lessons from speewa). Ours lives on the spare wheel on the camper's tailgate - that way it's right next to the kitchen for cooking scraps. One of the best things we've ever bough. As Teabag says, keeps everything messy out of the car, and away from the critters.
Mine is almost magical - it almost fell off the back of the camper last time we went away - arrived home to find it just hanging on my a thread. Would have been nice if it had dropped off - would have saved me having to empty it at home. The magical rubbish bag - rubbish goes in, and then it simply disappears...
Cheers!
Matto