9/10 a corgi installer won't finish off someone elses half finished work. a installer will like to do job start to finish, example - how does he know its secured to the wall properly and not going to fall off later, that the flue is going to exit the wall and be in regs.
for what time you can save him is nothing, let him do it all,then if theres a problem you can't get blamed.
hi-spec plumbing, May 2007