Keith,
I fully understand how you feel, bad service is bad service, i make no exuses for that, as for what would i have done, the same as you, complain, go through customer services, give them all the information you have, tracking number, poster etc, let them make their enquiries, on average it takes about ten days, hopefully in that time you have have received a satisfactory answer and outcome.
If you feel the customer sevice team have fobbed you off, or not taken you seriously, ask to speak to their customer service manager, I can assure you they do take this Seriously.
Regards
Gary