Yes, just to clear the air for everyone... I see absolutely no evidence to show that this particular James has been selling anything inappropriate on ebay.

I suspect he was mistaken for the individual selling the Ultimate Lockpicking CD. I don't think he's even on the same continent.
So... hopefully that clears that all up and somebody can get on to answering the question. I'm completely unqualified to do so, but that never stopped be before sooooo.....
James, seems to me that if all you're after is to make a safe, then really what you're looking at is making a box, probably with a swinging door, that can accommodate a standard safe lock. Look to a Sargent & Greenleaf model 6730.
As for the box.... a box is a box. There are all kinds of security elements in real safes that you could encorporate, but it depends on what you're after. Do you want something that is as close to a real safe as possible, and weighs several hundred pounds? Or do you just want a steel box that locks?
Maybe provide some more info about what you'd like to see when you're done and you'll get more help.
Cheers!
db