There are several threads on here about this subject, some quite recent so would be worth trawling through. In general there is nothing at all to stop you doing it and you would be paid ore if you can get the work but that's the problem. In many areas agencies have the monopoly and it is very difficult to get any work directly yoursel. I have sent dozens of letters out, been into schools and not had a single day's work that way. My agency keeps me quite busy though.