I have cut open the one bitbill and have the private key. I have registered with Mtgox with the username "ThisIsBTC123". Do I simply click trade, sell bitcoins, click add more (next to GBP in your account) and then under the add funds heading select "redeem private key" from the dropdown box? I assume this part gets the bit coins into my Mtgox account?
Once the bitcoins are in the Mtgox account and have been sold do I just request a withdraw after than (bank transfer)?
Thank you all!
You seem to be right on track. On Mt. Gox, under funding options you can choose to "Add Funds" and then select "Redeem Private Key". Type in the key that you found on the BitBills, give it a description (so you know where the money came from..not completely necessary, but still), and viola, the Bitcoins should be added to your account.
From there you can set up a withdraw method ("Withdraw" tab >> "Add Withdraw Method") to your bank account. It'll probably take a few days to process, but after that you'll be able to fund and withdraw to/from your bank.