Need advice from fellow contractors on agency fees.

[malvolio]

Actually it is just a tad over 16% - Very poor performances from you guys.

We are talking mark up - of the day rate offered

Only true if you found the business and engaged the agency. If you did, then it's up to you to negotiate a mark up rather less than 16%; in fact rather less than 6% would be closer to reality.

If you didn't, it's the agency's money and you get some of it; 85.7% to be precise (I hope...). As long as you think the agency is pocketing your money, rather than you pocketing theirs, you will always be upset.