Doesn't appear to be a third party as Amazon has their pre-order price guarantee applicable; also it says dispatched from and sold by Amazon. I don't care who sells, though; as long as I can get one and it pairs well alongside my Mary Poppins.
Its the same with previous Zavvi exclusives listed for pre order on Amazon the seller was listed as Amazon every time and they also included pre order price promise
What happens is your order get cancelled just before release date and then gets re listed after release date with the third party seller name listed
Have a look there are a few pre order BD Steelbook releases listed and these are Zavvi Exclusives
It's the same third party seller every time who Amazon list themselves as the seller when it's a pre order release and none of the pre orders get despatched
It will almost certainly be a Zavvi exclusive (along with Real Steel) as Zavvi is the only UK retailer to release Disney titles in the last couple of years. The OP did originally state that it might be a Zavvi exclusive but it looks like a mod removed that information.