Well everyone, I am very pleased to report that BA have settled with me and offered to pay the luggage fee and my court costs. They did so at the last possible minute, after indicating that they intended to defend the case. I wish they had admitted fault rather than continuing to deny it, but I got what I wanted.
I'm so glad I pursued this and would like to say a massive 'thank you' to everybody here who helped and advised me. The MCOL process isn't scary at all and I would highly recommend it to others in a similar situation. As previously indicated, I am going to donate the £65 luggage fee to charity so that something good can come out of this sorry affair.
Does anybody on Flyertalk have a suggestion for a suitable charity?