This is exactly what im saying about getting a USB EVDO connection card, and a EVDO Router. You don't need a computer at all, the router makes the connection to the EVDO card, and transmitts it to Wifi, and fits in the palm of your hand. It is battery operated, so all wireless (unless your battery runs out) and can plug up to charge
http://3gstore.com/index.php?main_page=product_info&products_id=610
That looks a great piece of kit.
I have never seen a router like that and didn't even know they existed. I imagine they are probably not available in the UK.