Noticed this in a Carphone Warehouse magazine I picked up running for the bus ;) (Can be seen on Page 57 latest magazine)
On Virgin, you can buy a Motorola V3 RAZR for just £99.95 (no quibbles!) You also get a whopping £40 free airtime, in effect putting your price down to just £59.99!
This is done by £5 is loaded onto the SIM, and instore they will give you an extra £5 free. Then, at the end of each month for 3 months you will be given £10 onto the SIM!
Addition: To my knowledge, this offer is INSTORE only and available at any CPW shop.