I was an O2 customer but phoned up Vodafone today and told them that I could potentially get £150 quidco if I signed up for a £30 per month 600 min/3000 text/500mb internet deal online;http://shop.vodafone.co.uk/shop/price-plans/24-months-600-mins-unlimited-texts-30?serverName=managed8
The guy spoke to his manager and agreed to reduce the rate from £30 to £26.43 per month if I agreed to sign up for the same deal on the phone. Quidco is great but I didn't want to risk not getting it. I still get a great deal, for a great phone, on the best uk network. I believe you can get this deal if you want it but it requires explaining the whole quidco thing and pushing it a little.... good luck
Before the usual crowd vote cold for the usual reasons please remember - a lot of the better deals on this site are via t-mobile (an inferior network IMO) OR require signing up through sites that have bad feedback.
Also my upgrade is available after 21 months - I am not fused about a longer contract when I know I am getting a great phone. I have had my SE k800i for 3/4 years now and I still love it!
I phoned up using this freephone number 0808 0000166 and asked to be put through to sales
I hope this deal helps someone out there :-)
p.s. I tried to get the twitter deal - contacted them a week ago but have heard nothing back hence why I acted and called vodafone instead