Can i go from normal sim to micro sim on the same contract?

I'm on a £7.50 a month contract with the samsung galaxy ace on Talkmobile with a normal sim but would love to get an iphone 4, would i be able to get a micro sim and stay on the same contract?

Yes. The sim has nothing to do with the contact. You just need to go to a store to activate it with your phone number

Yes. Generally you can ask the phone company to send you a micro sim, and when you get it there'll be some easy steps to register it to your old number. It can take anything from a few minutes to a day or so for the transfer to happen, mind you.

There are also if you're careful and impatient, instructions for chopping a big sim down to a micro sim floating around on the Internet. I don't think that's terribly wise, so I'm not posting a link, but it's an option if you felt you couldn't wait for the new one to arrive in the post.