Nokia Lumia 710 @ carphone warehouse - 24 month contract with 5000 texts, 100 minutes, 250mb of data and a free phone worth £110.
NEW WIFI HOTSPOT FIRMWARE NOW AVAILABLE FROM VODAFONE FOR LUMIA 710.
Not sure about other Mobile Networks. Installed fine using Zune software. Note this is note WP7.8 Update, but an earlier scheduled one.