I dont know about the money in your specific area, but for me when I contract it varies between 250 and 500 a day, with more recently me being on the bottom end of that as the market has kind of died on its arse.

Basically there are 3 reasons that companies require contract staff IME
1) They just need some normal skills but only for a short period, and the pay isnt anything special as although it will pay ok, you are in and out of work a lot and the periods out of work bring your annual income down
2) They need some niche skills that they dont have in house and are prepared to pay properly for it (this is the situation I was in when making 500 a day)
3) They just want more staff on the team without increasing the headcount for business appearance reasons (its a particuarly favourable thing in some industries to have a high profit margin per staff member on paper) this is a great situation to end up in cause you end up on contract money but for long periods of time

As for what the rates are for what you are going to be doing, you'll need to look around at what others are getting who do the same thing, but take with a pinch of salt all the adverts with agencies, ive seen adverts at 60 quid an hour and then when ive actually been offered the job the company is only actually paying 40, so a 50% "make it look good" factor needs to be taken into account potentially when viewing ads.