I saw the link today and wondered just how useful this might be. While it says the van pod can sleep up to 4, and there is an in-roof double, if there are only the two front seats left in it after conversion where are the others going to sit while the van is being driven? Ride their bikes?
http://www.youtube.com/watch?v=Q4qn0JGM__8
This was a pretty good video of it but I am still not convinced it is ready for the market. Price-wise especially.
Here is the Bike Radar article about it... http://www.bikeradar.com/news/article/video-doubleback-vw-campervan-33163/
Their photo gallery: http://www.bikeradar.com/gallery/article/video-doubleback-vw-campervan-33163/1
At GBP55k I think it is too steep for what it offers but I am not from the UK so don't know what kind of mobile home your GBP55k could buy.