During a previous life, circa 2002 until 2005, Ryanair worked with two recruitment companies, one being Brookfield and I worked for, indeed I became in charge of Flight Crew recruitment of, the other, an anagram of "morSt Aviation".
In charge of Ryanair's HR had been an individual, a man, with the initials DD, as if quite suddenly he was leaving Ryanair and he was looking to be placed with either Brookfield or my then employer, whatever discussions then took place were above my level and DD was subsequently placed with Brookfield.
Ryanair's agency rates were pretty much p1ss poor, as I recall EUR5 per hour for a Captain, EUR3 per hour for an F/O so if either worked to the maximum of 900 hours per annum one was revenuing just EUR375/EUR225 per pilot per month, circa 25% the revenue of pilots placed with other operators, the only way a company was going to make any money from Ryanair was by a significant number of placements or, indeed, becoming a "letterbox provider".
By my then employer's interpretation of the law the pilots could be deemed to be self employed if they operated from no fixed base, i.e. they operated from one base one week and another base the next and Ryanair abused this to the hilt, of course each self employed pilot was legally responsible for paying their own taxes and social security in their nominated home domicile, whether they opted to do so or not was none of our legal concern.
Once DD became placed with Brookfield their pilot placements with Ryanair went through the roof whilst ours remained constant if not diminished, I'm out of the industry now, I'm my own boss so I can say what the hell I like, quite regarding the legalities of what I have posted here is not a subject I care to be drawn on, I'm just saying how it was some 10 years ago, please respect my honesty.