electronicsuk,
regarding what my response would be, had the test revealed a leak:
First and foremost it is hypothetical now because I have doubts whether an adequate test was ever performed. If it did it, it seems quite a coincidence that it passed, but problems occurred with the pipes immediately on first running the boiler (remember that the Institute recommended running the test for a couple of hours).
But I will put myself in that position now. I would hope the test was performed BEFORE installation of the new boiler commenced, so that I did not incur any extra costs if it failed (I would like to hear a reply from any engineer on here who does not believe this is reasonable).
When it did fail presumably I would have the following options:
a) Not have the new boiler installed, but instead retain my existing boiler. There is clearly now a chance the pressure test has exacerbated pipe damage and it might still not work, but I would probably like to have the chance of trying it, on the basis that it had worked with the existing pipes before, and there is a chance that no further damage had taken place as a result of the test. If it subsequently failed then I would have no choice but to make a decision on replacing the pipes.
b) It is possible that the cost of repairing my existing boiler might not be cost efficient, so I would have to swallow the pain of getting the pipes repaired or bypassed. This is quite a feasible outcome, but the important point to me is that I can make a decision PRIOR to the installation going ahead, and therefore which option to chose, instead of being forced down the route of repairing/bypassing pipes, and I would know the costs involved up front (what is the point of performing a test otherwise?).
If the order in which the installation precluded a), I would question the procedure in which the installation took place, i.e. why was the test not performed first before any further installation took place (which seems like sound practice to me).
As I mentioned earlier, the company has been reasonable in coming out to fix leaks, but the cynical part of me questions why they are doing it (when their contract explicitly states that this work is not covered in the cost).
It is possible they know a proper test was not performed, and therefore have some liability. From their point of view, it would have been much better for the test to have been performed and show the problems first. For example, if the option of me retaining my existing boiler was taken up, it would be done with my consent and at my risk (with obvious chance of resulting structural damage).
As I mentioned earlier, someone else I know who had a boiler installed was made very aware when the test would take place, on the insistence that they were present when it occurred, and were also made aware of what would happen when it failed. I was not made aware of any taking place until well after it was installed, and problems became apparent.
The installer purchased the boiler prior to coming to installing, which is fair enough, I am aware that time is money. However if the procedure they followed meant that its' installation took place before adequate tests were performed, I believe then that is their responsibility.
Regarding getting other quotes, thanks for the advice, I have already contacted another (apparently) reputable heating engineer (who comes with many good references) who has quoted to perform the work for less than half the price of the company who supplied the boiler. He has also questioned some aspects of the installation and the advice I have been given by the installation company.