This is what I meant:
http://www.ebay.co.uk/itm/GPS-Antenn...YAAOSwvUlWqhyC
I guess that might contravene the Wireless Telegraphy Act, but since you're re-transmitting in to a faraday cage who is ever going to notice? The signals can't get in from the satellite, so they're not going to get out again either
