Shaun I am just going on what I have been given in the past by pretty much every company I've worked for. I didnt think I was fast and when I went for my last job o said to the boss I'm not the quickest but turned out I was the quickest by a long way.
I've always done copper very rarely used plastic as I dont think fitting plastic in an existing home is much quicker fitted properly.
Island you are paying british gas prices what do british gas expect from there employees. As kop has said you cant work them flat out all the time but if they are getting paid well I would expect them to work hard 90% of the time.
Personally I would pay bonuses for jobs completed on time and with no call backs. If you put people on price they chuck things in to get to the next job.
Gasmk1 3 hours to fill a system? Wheres that Buckingham palace?
the last time I had a system take over an hour to fill was about 5 years ago in the end I repiped the cold feed and vent then it filled within 20 minutes.