Now I've tempted you in I'll fill you in on the proper details. The phone comes from a site called smartfonestore and they sell on phones that have been returned because a customer wasn't happy with it and so can't be sold as new, or phones that have been recycled. They have two grade B Xperia Z's left which are both SIM unlocked
http://www.smartfonestore.com/buy_Handset_Sony_Unlocked_Xperia Z_Black_B.aspx
Grade B generally are extremely good condition. I've seen 5 grade B's from them and 4 of them looked almost brand spanking new, and the other had a few scratches on the screen. If you get a phone and you're not happy with the condition of it they offer free no quibble returns within 7 days of getting the phone, and it's all done by RM next day delivery.
As for that tariff, here it is
http://giffgaff.com/goodybags Giffgaff are an MNVO run by O2 and I can refer you if it interests you?