Merrick, I can't find any info on this that would help you. I can find BioShock 2 support phone numbers for US and Canada, but not the UK.
I did find an advocate email on their website:
We are currently making improvements to our customer service. If you have reached out to customer service/technical support and are unhappy with your experience or do not feel your expectations have been met, please reach out to our 2K Games Advocate at www.2kgames.com/advocate.
I don't know that they can help but it won't hurt to send them an email.
Have you tried to remove the mark on the disk?