I've managed to get the CD out now so turns out not such a bad buy after all :)
Works well and integrates with my highline too as I'd hoped after reading other forum entries. Have to say very pleased with it. Be happy to help with advice for anyone else looking to do the same thing now after worrying so much about battery drain. From what i can see so far, no noise coming from it while the car is off that would indicate its drawing power and once I get sat nav coded, will update after that.
Thanks Scopes and Rossimac for your replies