Just called to request the unlock code for one of the phones I got on the HUKD from tesco direct (1112) & got offered the above - no cost & still getting the code (their version of retentions it seems!!! ;)). I stuck the £30 worth of vouchers on last night - get in quick if you want to unlock - their T&C seem to have changed - from free after £30 credited to after a period of time and/or fee (both undisclosed).
Seemed very helpful & at 20p per call list out any questions to get them all for 20p. They asked for the mobile number & IMEI (*#06# on the keypad to reveal it). (Plus the usual name, address, etc.)