Hi Tomm,
We used Interparcel when we sent my daughters visa application to the British Embassy in Manila and I booked it online. I had already checked the prices of most of the couriers online and Interparcel were much cheaper than DHL, but guess what, when the courier called to collect the package it was a man in a DHL uniform in a DHL van that came to collect it.
I also managed to track it online on the DHL website and it arrived at the British Embassy in about 36 hours.
Cheers,