Screen problem after Home Button Replacement

Hello Guys,

I have acquired an iPhone 4 after my wife has upgraded to the new model, however the home button was very intermittent, so I replaced it and it now works fine. However the phone turns on and looks fine, but when I try to scroll or press to go to an app, it either doesn't respond, scrolls really fast or too much or clicks on something different. Any ideas?

Thanks in advance for any advice.

Tom