I think the VW stuff would be prohibitively expensive and tied in with having a 'Phone Prep High' installed.
I wouldn't get too excited about 4G either, there are lots of hoops to be jumped through before it happens and also it will take time to roll out. EE claim to have '16 Cities' by the end of the year but I can't see coverage being too special from the outset. Lets face it their 3G isn't startling.
How about -
http://www.kufatec.de/shop/en/car-wlan/ ... MTS-router
IMHO you need something that is going to 'appear' as a phone to the Service Provider to avoid or at least minimise monthly charges. Something like 3 Ultimate Internet SIM 200 1 month for £12.90/Month which includes AYCE Data.
I've ordered 3G MMI Sat Nav with Audi/Google Online Services for my A1 which comes in the guise of Phone Prep High so I will be looking at something similar myself.