cavity insulation disaster

From my experience I would advise anyone considering the Mark Group for cavity wall insulation to steer well clear. My bungalow had one of their installations in March 2009 and the whole process turned out to be a sham.
Two years after the work was carried out I had all the windows replaced in my bungalow and it came to light that 75% of the cavities had no insulation in them at all, the parts that were filled had mould growth on the internal walls..
The Mark Group upon inspection had no explanation as to how this could happen and when asked why they never checked materials used against the materials required, as they should before issuing their guarantee, they had no answers.
They have offered to remove the insulation they did manage to get into the walls which is causing the mould growth internally but I don't think I could trust them to carry out any more work here as their incompetence seems to be endless. Has anyone had this done I would be interested to hear.
Finally from my experience either I am the most unlucky house-holder in the country, if this is a one off event, or the whole cavity wall insulation idea is a big sham which should be investigated by someone other than the industry itself. In my opinion they must be ruining thousands of properties year on year wherever they go.