Replacement screen not responding correctly

I replaced the screen for my iphone a few days back after smashing the previous one. Since then it hasn't behaved itself all that well. Sometimes I have to swipe right a few times to unlock the screen, and when typing a text/email/status etc I may try to type an 'A', and instead the 'C' will be selected and 'held' so it prompts an alternative language key such as ç. Other times it will be absolutely fine, but I probably experience some kind of minor inconvenience at least once a day. At least I can see the screen, but how long before I go all Basil Fawlty and smash this one in frustration? I'm wondering if the problem lies in how I installed it, or if the screen itself is the problem.

http://www.ebay.co.uk/itm/331161689457?_...