TNT - how do I complain

TNT have set a new standard of incompetence. My passport was printed on 30th March and I was able to track on 7th April and the delivery date kept moving and its impossible to talk to anyone. I tried to collect it as depot is close to me but it was already in the van and Id have to wait 3 days before I could come and get it! Imagine my horror when I got the photo showing they had delivered it to the WRONG ADDRESS - i live at 2a as was clear on the address etc and they delivered to 24. I went to the house and it looked like they hd gone on holiday . I couldn't speak to anyone at TNT and the robot just stops you speaking to anyone. My passport was at the wrong house and I couldn't do anything about it. And the residents, according to the neighbours, go on holiday a lot and no one had a key! It was a long wait and luckily the residents came back at 8.30pm and brought the passport to me. Whilst I am relieved, I really want to complain and flag that TNT are incompetent and impossible to deal with - to put a legal document like a passport through the letterbox of the wrong house (clear on address label) is beyond belief especially at the start of the Easter Holidays - if they had already left for holiday, I would have lost 3k as too late to cancel my holiday in 2 weeks time! Does anyone know the best way I can complain?