Same deal as has been on numerous times before.
The phones offered for free are:
- Samsung Solid Extreme
- Samsung Monte
- Nokia 5230
- Nokia 6303
- Nokia C3 (Pink)
- Samsung Monte (Pink)
- Sony Ericsson Elm
- LG Viewty Smile
- Nokia C3 Slate
I believe the most valuable for trade-in is the Sony Ericsson Elm, which you can currently get ~£50 for @ CEX. Significantly more on ebay.
The Nokia 5230 looks interesting too, especially as Nokia's Ovi Maps can work adequately without a data contract. Though it unfortunately lacks the wifi connectivity of the Elm.
Last time this cashback deal ran I had no problem with cashback paying out in full. (infact, it paid out too much; £240 in total - subsidising my entire contract :)
Link to Vodafone's Quidco page:http://www.quidco.com/vodafone/