There are currently 4.5 million people on benefit of one kind or another. There are currently 400,000 jobs available nationally. Even if you strip 3 million of those people out for whatever reason, there is still a shortfall.
The jobs market is brutal at the moment, and every vacancy is inundated with applications. The law states that jobs that are advertised internally also have to be advertised externally, so a lot of jobs that are on display are already taken.
It's horrible to be rejected but sadly that's the way it is right now.
Update your CV, post it all over the internet and apply for everything. Eventually it might work.