I think you'll find the said agencies require you to sign a contract that you will never attempt to claim "equal rights" with permanent staff.
ie - no paid holiday, no sick pay, minimum wage, no overtime rates.
Its called the Swedish Derogation and makes a mockery of one of the few decent laws Labour did enact in 13 years.
I know people have to use them but as far as I'm concerned employment agencies for low-skilled workers are parasitical scum. I'm no socialist but the employment agency will be making more money (gross) than you snadge, they're probably on £15/hour for those positions.
Never heard of Swedish Derogation before today, but quite shocking. It seems comparable to the antics of Company pension trustees, employing clever 'spiv' lawyers to find an angle that turns well-meaning legislation around to their own advantage.
Once upon a time (and in my life time), the legal and banking and Industrial sectors could be relied upon for a degree of gentlemanly contact. Not any more it seems.
I'd like to think the Spivs who dream up these schemes would one day be knocked from their perches, and held to account. And, like Nuremberg, 'I was only obeying instructions' would not be accepted as a valid defence.
Sorry for the rant.