Doing what’s asked of you can occasionally involve running bent. Eg. You are due to leave a depot 3 hours out from base. You are currently 12.5 hours into your shift. Firm orders you back, because as agency you might be paid the full whack for your ‘night out’ - that is, the 9 hour rest break, and the flat 8 to get home next day, despite it only taking 3 hours to get back.
Firm doesn’t fancy paying that, so they’ll ask you to set off back, knowing you’ll run out of time… Initiative - I’ve volunteered to do the “night out”, and had it thrown in my face more than once in the past. Yet, I still get asked to do the impossible run back on “same day” basis… FFS! I’ve been flexible, in offering my services beyond the call of the original duty, but the firm just want to save money, even if it involves ordering me to break the law…
An example of “making the customer happy, and ■■■■■■■ off the consultant” would be taking on a private contract between yard and myself because the firm want me for a 3+ week block of work across Easter, Christmas, etc. which the agency have already told me “isn’t available”. Now, the agency are supposed to get a “finders fee” for this sort of action, but if it’s a deal betwixt myself and the firm, that isn’t going to happen, thus the “consultant” is ■■■■■■ off. 
I do supermarket work, parcel trunks, food trunks for non-supermarkets, and very occasionally some sub work like RM on the runup to Christmas.
I don’t do “exclusively umbrella” stuff like Iceland, Nisa, and other high street non-food stuff like Tkmaxx, wilkos, etc. They’d have to double the hourly rates to make me even look at it again. 
Agencies are here to stay. A symptom of the so-called “flexible jobs market” that the government wets its pants over, but shafts everyone actually trying to get a full time job.
…But without them, they would be queues at yard gates, like the 1930’s when there were no such thing as agencies, but still no full time jobs! 
Gone are the days of “bribing the foreman” I think. 