OK, time to explain how Investment Banks run their IT departments...
most of the staff are contractors, they are usually on rolling 6 month contracts. When things are going well, the contracts get rolled, but as soon as the markets are down the banks can get rid of them far more cheaply than they can permanent (employed) staff. As some form of compensation, the hourly rates are higher, so a contractor may well earn 10-15K more than an employee.
Being a contractor.
You either set up a company with yourself as the director, and invoice the company you work for, or you are self-employed and receive the money directly. My tax exams were a long time ago now, so I won't list the differences it makes!
IT helpdesk...
If this is anything like the ones at my work, the real IT departments ( ie the ones that do the work) are divided up between various systems, server/networking and desktop support. If you need anything doing you have to log a call with the helpdesk first. They then pass the message on to the relevant department.
The helpdesk staff don't need any technical knowledge, but do need patience to deal with stressed/p***ed off people who's computers have just crashed again.
Valky