Powering a 350D from a cigarette lighter adapter

That's a good pdf link there Steve.
Building the regulator is trivial, what's a little harder is getting a dummy battery pack to fit into the camera, as it happens my battery is shot so I'll be dismantling it and using that as the dummy.
All the regulator parts can be got out of maplin.

I use a battery grip which has two batteries

Likewise here. It only adds a little over a half pound more in weight. But does the job (it also takes 6 AA batteries in lieu of 2 Canon Li-Ion batteries too). Much safer than messing with mains currents and cigarette connectors.

Seanie.

Dave... any chance of making 2?

You will be suitably rewarded!!!