** Update **
Well, 8 weeks went by with no response from Qatar so I filed a complaint with the UK Retail Ombudsman, who:
"We hear complaints about member and non-member airlines. Our members are bound by our Code of Practice and Membership Rules, part of which states that they will be bound by any decision that we make.
Non-member airlines will not be legally bound by our decisions, although it is likely that they will observe such decisions. However, on occasions where we find in the consumer's favour and the airline does not observe our decision, consumers can take their complaint to the small claims court armed with our decision."
Turns out Qatar is a non-member so I didn't expect an enforceable decision. I lodged the complaint, received a reply later that week saying that they had contacted Qatar about the complaint and were waiting on a response. Then after two weeks another reply from the Ombusdman saying that as Qatar is a non-member they can't help and have closed my complaint request!
Meh!
Next step is to file the complaint with the UK Civil Aviation Authority, Passenger Advice and Complaints Team. Again, not enforceable or binding on Qatar but useful if I go to the small claims court.... If the CAA go the same way as the Retail Ombudsman, then I'll bit the bullet and give it to a 3rd party agency for collection (at 30% commission)...