Costly, ignored specification, rude
My experience with this company has left a nasty taste in the mouth.
First, cost. I got them to fit a single secondary glazing unit, approx. 1 x 1½ m., which turned out to be two hours' work. For this they charged £960 + VAT. When I enquired (so as to be fair to them) how much of this was labour costs, I got a rude email back saying it was confidential information. It's hardly surprising they don't want it known, though, as it must run into the hundreds per hour. Makes lawyers look cheap!
Second, negligence. Sash windows open inwards on hinges for cleaning and repair, and I specifically asked that care be taken not to impede this. But the width of the frame on the new unit they installed permanently blocks it. (You can still slide the sash up and lean out: over a 25-metre drop to the pavement below.)
I suspect firms like this can't really be bothered with small jobs, so they just milk them for all they can get and tick them off without much concern for the detail of customers' wishes. A pity: I was pleased with their brisk initial response, but I'll be looking elsewhere for glazing in future.