I think loyalty went out the window as soon as the recession started and money got tight. If it were me, I would post an anonymous letter through the door stating the faults and possible problems that could arise.
This MAY worry the custard enough to call the installer back which will serve him right, causing him some grief and maybe making you feel better.
Failing that, use a freeze kit on that poor condensate, that will get em back
Thats actually not a bad idea.
You could set up another website and email address for correspondence.
Have some report form type stationery printed and if you see something,write a brief report and mail drop it.
If everyone did it it would have a few effects..
1)Rubbish installers would take some heat..
2)You would likely benefit from some remedial work
Remember,,those Nigerian scamsters send out thousands of letters and emails and get a good return rate so this could be a new income stream.