Currently Being ModeratedOct 31, 2012 3:33 AM (in response to jjmiltonkeynes)
You are lucky if you have managed to create a recent backup of your device. Simply restore your phone from a previous backup and this should bring your data back. You may check your previous backups with iPhone Backup Extractor. Also try checking if your contacts are synced with contacts manager as well (Google, Yahoo, Outlook, etc.), you may be surprised that they are there. ;)
Currently Being ModeratedOct 31, 2012 4:25 AM (in response to jjmiltonkeynes)
Have you enabled iCloud after updating your iPhone? Do this now and you should get back your contacts. If your AppleID is not @icloud.com or @me.com your notes are not saved in iCloud and can only be restored when saved in a different location like karenmillares suggested.
To enable iCloud:
Go to "Settings" > "Mail, Contacts, Calendars" and check if you have an iCloud account added. If so check if Contacts are enabled for that account.
If you don't have an iCloud account added yet just use "Add Account...", select iCloud and use your AppleID credentials.