No I am self employed now doing the thing I used to do as a temp!
The temping part with all the different places to work at did allow me to build up VERY wide experience so that I am better at it self employed than others like me I have come across. Also, I do the self employed for smaller businesses that can't afford a 'me' full time. (I am a credit controller for smaller businesses).
I used to temp because my 'main' job was doing site accounts for construction companies, so each time a 9, 12 or 18m job on a construction site finished, I'd do office temping for a change till the next longer term project came up. Some agencies practically rolled out the red carpet for a temp who was always on time, picked up the work quickly, worked the hours required and didn't think that being hourly paid meant 'work whatever hours you feel like'.
Others though would bung you in any old job and lie about the duration, cos that was easy money.
Now then, temp agencies are USED to temps leaving because they get a permanent job or they only want term time work etc etc. So what I'd do if I were you is ring them up the next time you're in the office and say 'I am sstill not happy here. Can you find me something else?'
Then ring a couple of days later and ask if anything else has come in yet.
Then in another week say 'I am not being stretched and the money is not so good. You told me it was only for a few weeks and I am still here months later. If you don't find me something else more suited to my talents and skills and more money, then I'm sorry I will start registering with other agencies that can'.
Another thing you can do, if its just the money is tell the temp agency that if they want you to stay all this time then you will need a bigger cut of whatever it is that the company pays for you. I did this once and it worked. If you find another job remember that the rate from the agency is NEGOTIABLE and they will always offer you a lower rate at the start and probably find another pound or so an hour for you if you put in a good case.
Or you can go to your boss at the employer and explain whats going on. Ask if, over the summer they might be taking temps on for anyone's holiday leave cover and ask if you can maybe have a change of role for a while? Or first dibs on any better roles they may need a temp for in other departments?
Temp agencies are there to make money. They sometimes forget that happy workers = more money for themselves so maybe its time to remind them. What agency is it btw?
Some of the best to work for were either the higher-end accountancy firms, or the 'bottom end' (of the payscale) secretarial agencies like Kelly or Office Angels in Manchester, although those were in the early 90s so may not still be around. They treated good temps like GOLD DUST but I think things have changed now because there are so many people unemployed.