You see a lot of examples of that in the Jeremy Kyle generation.
There are a significant minority of brits that are generally quite lazy and used to getting what they want with little or no effort. The welfare state was initially formed to subsidise, not fully support low-income families. The brits don't want to work in low-income jobs and, as you pointed out, there is a ready made workforce which employers are more than willing to use and abuse.
I believe that we have a responsibility to support the genuinely needy, I don't believe that we do that effectively.
It's the same in the States, General Motors are closing plants in various regions because of the $15 dollars per hour, they railroaded migrant workers into doing it for far less and are using their financially doped, tax-break muscle to hold the government to ransom.
Nothing new there, it's happened here for almost 3 centuries.