K5 Change Waterstones Kindle to Standard

Hi Folks

Being in Belgium I couldn't by a Kindle Paperwhite from Amazon, but instead got one from the Waterstones bookshop here in town. What I didn't know when I bought it was that the software is Waterstones branded and I'm missing out on the standard Amazon sleep screens. This really annoys me.

Now I've seen plenty of threads about hacking the picture, but what I really want is to convert my Kindle into a standard Amazon Kindle.

Is this possible, perhaps by factory installing with a suitable firmware image?

Cheers
Dave