In my experience
In my experience, this company makes basic technical errors and then shows no regret and no particular hurry to sort things out. All but one of the ceiling valves for my mechanical ventilation system were fitted the wrong way round [extractor to supply outlet, supply to extractor] causing down draughts that put my wife through two years of repeated sinus and ear infections; a day timer was set from 7 am to 11am, presumably because the installer didn't notice it was a 24 hr clock and actual flow rates were different from those on the original commissioning certificate. It took over 4 weeks of largely ignored telcalls and emails to get all the valves changed and 8 weeks on I am still waiting for the recommissioning certificates to check the new flow rates etc, with the manager saying he can't give my job any priority "with everything else going on".