ok, well what id would do is call orange customer service and say youre gonna leave at end of contract, hopefully they will want you to stay and then you can see what deal you can get. Use an example of a cheaper provider. I just got my parents an 18 month contract with vodafone for �10 a month including free eve and weekend calls and free texts (200 i think).
the worst they can do is say they wont give you a cheap deal (make sure you ask for new phone too, but you wont get anything flash) and if they wont then shop around.
The websites for the main providers are a good start. Oranges cheapest plan online is �15 a month but sometimes you can get better rate if you call them.