This posting on MSE gives an address:
http://forums.moneysavingexpert.com/showthread.php?p=40514326#post40514326 Quote:If you write those things on a piece of paper, I'm more than certain that it will be OK but if you still want to make sure, their helpline number dedicated to the BIC challenge is 0845 026 4559.
The address to send off your pens to is:
Challenge BiC Promotion, PO Box 1079, Hemel Hempstead, HP1 1GY
Putting the post code into Google reveals many competitions that all use the same PO Box 1079, including big name brands such a Macleans and Knorr.
One such promotion is for
Tesco which gives the contact number as 0845 026 4558 - that's one digit less than the one for BiC Challenge. So I suggest that the 0845 number is operated by (and therefore probably goes to) whatever company the PO Box belongs to.
If someone can come forward with the name of the mystery company, then we may be able to get somewhere.