That second audit has now been questioned on many grounds including the fact that, through a set of careless procedures, the observers could have been duped when selecting a random sample of centres to audit.
From the people who join the page I'll be selecting a 'stratified sample' (that's my statistics GCSE maths coming in there) to analyse for my experiment.
In the sample of of files reviewed, we noted that the main criterion for selecting a particular contractor appeared, in many cases, to be the purported availability of the contractor to commence the works within a reasonable timescale (which Property Conservation officers advised us in interview was considered to be approximately six weeks from instructions).