Seriously, I've no idea why you agreed to pay that for the work. You could have bought a replacement engine for less! 
Gutted though mate 
Couldn't go anywhere cheaper?
The issue I faced was I assumed it was related to the cock up the month prior there for assumed the warranty covered it. I was wrong

If I wanted to take it somewhere else they would have had to put back the dud cylinder head charging me for the diagnostics costs at 5*£90. They didn't charge me for removal, kindly gave me trade price and reduced labor cost.
Whats saying a second hand replacement engine wouldn't cock up down the line.