"But I got the postcode from the Post Office - surely they are the people who do post-codes?"
"Sorry sir - it's not the one engineering have on file for that building"
"OK, to avoid this happening again can you please tell me what post-code engineering have on file so I can re-schedule the job and be confident it won't get bounced back again?"
"I'm sorry sir, engineering won't disclose that information"
Eventually I did get the line installed and the day it was livened up I found myself sitting on the floor of the client's comms room with my laptop connected to the new router and no return pings from their end - I could see a carrier on the line, but no data. So, I called BT again and gave the various job numbers etc. and got the reply:
"I'm sorry sir, that line isn't due come on line until 2099"
He honestly said that without a hint of irony!