I had a similar experience with Tescos with a badly scratched DVD that I
bought from them. First of all the customer services representative said
that I had probably scratched it, to which I replied that as I wanted a
replacement DVD this would be of no benefit to me so why would I have
done it? She then agreed to replace it, however each of replacements of
the same title from the shelf were also scratched badly in the same way.
The member of staff was now looking even more embarrassed of have
accused me of scratching the disk. So failing to get a replacement I
asked for a refund, she then told me how it was company policy not to
offer refunds on CDs and DVDs. I then reminded her of the sale of goods
act and that regardless of "company policy" I was entitled to a refund.
She then agreed to a refund but she had to run it pass her supervisor first!

It seems as though Tesco cares little for consumer law unless the
consumer knows about it. I will certainly not be buying anything but
food from Tesco in the future as Tescos idea of customer service is
obviously that the customer provides the service of lining their pockets
and that's were the relationship ends.