Apologies if this subject has already been covered on the 'B&Q Compost Issues' forum thread. (There are so many posts that my computer jams trying to get to the end of the large number of comments on that thread).
BBC website (under Scotland tag) has article by Eleanor Bradford, one of the health correspondents about a health warning and possible (but not 100% proven)link with compost and strand of legionnaires disease which seems to relate to Scotland only. However, the report does briefly mention changes in manufacture of compost but not in detail. It may turn out that the source will not be the actual compost (ie legionnaires carried on water droplets etc) but whether scaremongering or not, it's perhaps interesting that compost was linked with the report subject. Perhaps it will open up further investigation into the compost production issues.