I wonder if the Blue Peter competiton winner will get any money from its sale.
Nope. Standard contest entry rules. All entries are property of, in this case, the BBC.
And while the Junk Tardis does look nice, it's a really lacklustre paint job on the console when you take a closer look. They couldn't even be bothered to put a reflective surface on the mirror, which was actually what we saw the most of in the episode, with Idris looking at herself. That, and the lack of an Idris figure with it took it from a "must have" to a "maybe somewhere down the road" for me.