I had the same problem, and after a call to an unhelpful o2 person, followed by a web chat with a helpful o2 person (who gave me the info below), I can confirm that this has allowed me back into my account...
"Wait 24 hours, you can then reset your Blueroom password by loading the O2 Website (
www.o2.co.uk ), click the drop down box next to Explore, click Blueroom, click find out more under Priority Tickets, click on sign in at the top of the page, click on forgot password, enter your mobile number and click on 'Send Code', enter your code and click continue, you'll then be able to reset your password."
...shame it took 24 hours, the priority tickets sold out!!