By law you have at least 12 months warranty on anything purchased. The actual wording says something woolly like "reasonable time" or something like that.
Anything extra provided by your credit card company or the phone manufacturer is in addition to your statutory rights.
The place you purchased the phone from is responsible for the repair of the phone. Repair is the only thing you are entitled to after 30 days. The supplier can at their discretion issue you with a replacement phone - but this will not always be a new one.
If they try to fob you off by telling you to take/send it to a service centre, this is illegal. Your contract is between you and them as a supplier.
As you purchased online there should be a paper trail to follow.
First thing I would try is contacting Orange. They should have a record of the transaction with the date it was made.
Second you should look for statements from your credit card which should show the transaction. This will be enough if Orange demand that you provide a proof of purchase. However as it was an online purchase it shouldn't be required.
Check the Government's excellent consumer rights web site at
http://www.consumer.gov.uk/consumer_web/index_v4.htm for more information on where you stand.
Simon.