Ok! The Freeview box is a BT iPlayer there is a link to a review here:-
http://www.radioandtelly.co.uk/iplayer.html
In this review it gives this information about the USB:-
USB Port The iPlayer's USB port allows connection of hardware such as a wi-fi or ethernet adapter (for broadband), printers, USB drives (for accessing files), memory card readers and webcams. A series of built-in drivers support a wide number of USB devices, but as it is not possible to install new drivers, not all USB devices are supported.
Note that it is not possible to use the USB port to stream video onto a disk drive or network - the port is to connect add-ons to the iPlayer.
Technical Specs USB: 1.1
The vendor replied to my help request and has very kindly offered to replace the MP4 Player, I have already posted it back by signed delivery to Hong Kong.
I must say this level of after sales support is great and shows that international ebay sellers have an increasing level of integrity and customer service.
After this experience I won't be trying to charge the replacement via the Freeview box, it will be by PC only!
All's well that ends well!