I worked for a charity whilst claiming JSA, under a Job Centre promotion.
The idea is to reintergrate you back into the working world, whilst I agree the hours seem quite drastic I do think this is a good thing.
Got offered a paid job at the end of my time (about 5-6 weeks of 40 hour weeks) but had also got offered a job at my current employer on the same day so took that. I have no doubt that the temporary JSA/Charity work was the main contribution to getting the job I have now.
I've done this in the past too. 30 hrs per week sorting stuff in a charity shop. I asked to help out with the doles (intraining) IT course to teach those who are not computer savvy, at the time, nothing was offered in that regard... so much for big society.
I guess the private company running that side of things didn't want to share

What I do know is that all of these places get paid by the government for you being there (not the charities etc, but the private businesses running the dole schemes and those taking workers on). I don't know specifically how much, but I've heard rumours of 2-5k all the way to 30k for each candidate, whether that's for 6 or 12 months or a one off payment, I don't know.
In principal, I have no real objections to some of the welfare to work ideals. However, the reality is as follows -
Take a company like caterpillar.
Make a load of their expensive full time staff redundant.
Sign up to government dole work scheme.
Get YTS people to do the work previously occupied by your FT staff.
Rotate candidates every 6-8 weeks with no promise of a full time job at the end of it.
Get paid by the government.
Pay YTS less than you paid your FT staff. (essentially dole)
Profit.
Exactly this happened to my cousin; he was made redundant and was replaced with a load of YTS blokes from the dole who then get cycled through the factory then shuffled out of the door. Caterpillar make money, the dole get to look good, the full time staff loose their jobs (some of them even ended up on the same dole scheme...) and the YTS blokes are no nearer full time work than they were before. So it would appear that the scheme only benefits the government and the businesses. And lets face it - all of these private companies involved with such schemes are not in it because of their altruistic nature. Quite simply they expect to make money, quite a lot of it, out of a government subsidised work program. They would not be doing it otherwise.
Big society as an ideal encompasses many things, one of which is getting local people to do useful stuff locally. This is a good idea.
But with anything connected to the DSS, it will prove to be an unmitigated disaster, chiefly because of private business chasing money, whilst front line JC staff and those on the low tiers of companies like intraining, have their hands tied by the bungling of their senior managers, who's mandate is to follow the money, rather than facilitate introducing someone with a skill or an idea, to someone else with a problem or a task.
In principal, it's a great idea. The reality will fall somewhat short of the intended mark.