On a side note, on of the guys has been contracting here for 6 years.......I have no idea how thats acceptable.
Why isn't it acceptable, the length of time is pretty irrelevant, its all about how you work. If he is working as a disguised employee, and is claiming he is outside IR35 then thats a different thing altogether.
Someone can contract for a single firm forever if they are inside IR35 or doing it via an umbrella