It's just a natural result of the downturn in the building trade and a result of fear factor of the recession. The demand has dropped right off for all trades, and the people wanting refurbishments and new bathrooms etc simply either do not have the money or are too nervous about their own jobs to splash out. Established plumbers are finding it hard enough at the moment so new entrants have even less chance of success.
The training centres jumped on the back of the boom in the business, and like the rest of the trades are suffering.
There is a knock-on effect with suppiers as well. As we all know, Plumb Center has closed loads of branches due to downturn in trade. My local merchants has shed half the staff and two years ago you used to have to queue to get served and now you are often the only customer in.
All those Polish plumbers seem to have disappeared too.
On the other hand, don't knock the people who go on the short courses with no experience - gives us plenty of work putting their jobs right after they have finished!