I just purchased this: Amazon.com: Kensington K33197 120W Auto/Air Ultra Portable Notebook PC Power Adapter: Electronics which requires a Cigarette Port to use.
I was wondering is there a good adapter that would allow be to use this devise in the home aswell with the mains? (I'm from the UK btw).
It's just an inverter, with the usual current protection stuff etc in. I can't see why you'd want to use that indoors, using a transformer to step 240v AC to 12v DC to then step it back to 240v AC seems more than slightly energy inefficient.
Yes, it's possible though. Personally, I suspect that you won't find anything off the shelf because it'd be completely pointless and nobody would buy it. You could probably make something that would work if your rummage around in maplins though. It's not like you can't pick up 12v dc transformers off the shelf easily enough.