Enterprising Hackintosh forum member erhnam was rooting through the iPhone's firmware and came up with some files that might indicate exactly in which direction the European contracts are going:

Default_CARRIER_ATT.png
Default_CARRIER_CINGULAR.png
Default_CARRIER_TMOBILE.png
Default_CARRIER_VODAFONE.png

Latest on the rumour train is still that Apple will announce the Euro iPhone when sales in the US hit one million, with analysts heavily tipping Vodafone and T-Mobile as carriers of choice.  It's looking more like initial suggestions of retailer The Carphone Warehouse setting up as some sort of MVNO were overstating matters; instead, it's not unknown for them to secure exclusive distribution deals for handsets, and potentially they'll be doing the work of Apple stores in the US (there are only nine Apple stores in the UK).

Hackintosh [via Engadget]