i have never been paid more than a full time bod only ever been on parity pay. The reason some think they are on more money is they are on a umbrella scheme that pays a pound or so more to cover holiday pay and employers ni not to mention the charge to be paid (it doesnt cover it by a long chalk).
When you get down to the nitty gritty those on umbrella pay are far worse off than full timers or paye agency
Ps some agencys say it is paye but play the same game