Hi I dropped my iphone 5 and couldn't afford to replace it so have got an iphone 4. As the sim cards are different I've a new sim card and have lost most of my contacts. I had the phone backed up a while back but even really old contacts are gone.

I am not sure what you are asking, but if you backed up your iphone 5 to icloud when you set up the 4 you could restore from icloud backup.

MACOSX24

The iPhone does not store contacts on the SIM card: http://support.apple.com/kb/HT4994?viewlocale=en_US

You may elect to sync your contacts in the cloud to avoid this issue in the future.

Contacts aren't stored on the SIM.

Just as the other two said, the Contacts aren't stored on the SIM card.

So what have you done differently from the 5 to 4 as far as signing in under

Settings---> Mail, Contacts, Calendars---> Accounts???

KOT