Well done on the pass John.
My experience of agency work, like Jonboy, is that although the agencies don’t usualy want you to do assessments, many of their clients do. It’s usualy a formality ( tho’ not always) so they can tell their insurance co’ that your driving was assessed. Just tell your assessor that you haven’t been driving long and drive the way you should. 
Once you start getting work, thin out the agencies which don’t give you work or give you bad paying/impossible to do, jobs. Even if you make a right pigs ear of a job and the client refuses to pay, you are employed by the agency and so should be paid whatever happens. If they give you to much grief, or won’t pay, drop them quick. 
(This happened to me. I was given 22 drops round Glasgow city centre, in a clapped out old fridge wagon. I to follow a set route, doubling back and crossing over where I had already been. On top of that, most of the addresses where wrong in some way. I got 17 of the drops off and called at 3 more but couldn’t make the delivery for some reason. I did a 15 hour day, plus an hour each way travelling. The client refused to pay the agency, so the agency refused to pay me, then had the brass-neck to phone me to do a job 2 weeks later. I answered that, “yes certainly I would do it, as soon as I got paid for the last job”. P.S. That job was on the 22nd of Dec). 
Once you get settled in, you only really need 3 or 4 agencies which give you plenty of the type of work you enjoy the most. That way you can play them off against each other. Be careful not to muck them about too much though, or you will only get offered the jobs that no-one else wants.
All the best, and keep us up to date on how things go.
ask ur instructor if he knows anyone who might take you on; it worked for me!