Thanks for all the input.
To be honest, i'm surprised at the lack of support and logic applied from Qatar.

After speaking with them today, they advised that the held booking price changed as the ticket had to be repriced as I payed it over the phone! After explaining the situation, I was basically told that it is not their issue that the online payment didn't work and that I would need to follow up with Mastercard secure payment as it is not Qatar's issue.

Amazing!