As said before, how long the job takes down to the minute, is frankly none of the customers business.
Obviously. Why should the customer bother or even know that he pays an inflated hourly rate?
Hire a polish immigrant and put him on an hourly wage where you manage the job start to finish and buy materials yourself. Remember you'll need to pay him to come out and quote the materials for you. It'll probably cost a lot more than £200 to get the same result but at least you'll not feel ripped off.
If the joiner had bought the picture rails, then the 200 Pound would have been absolutely fine, and I would've put an extra 10 or 20 Pound on top. But that wasn't the case.