I don't know if this is well known but I couldn't find a topic for it. Went in to Orange shop the other day to upgrade my contract which was in its last 2 months. Took them a while to offer this but eventually they told me that if I return my old handset from the contract I will get £100 off the overall total of my contract. Works out to roughly £5 a month so my contract is now down to £14.
Best thing about it was that all you need is the handset, no accessories, box or charger are needed and doesn't matter what condition the phone is in, as long as it switches on. Has to be the original handset you got with the contract though. Hope this helps some people out.