For Android 4.0, 4.1 & 4.2 Jelly Bean & ICS Internet and MMS Settings,
These settings are subtly different to the ones for previous versions of Android.
Go to Settings.
Choose More Settings.
Choose Mobile networks.
Choose Access Point Names.
Press the Menu button on your phone and choose New APN.
Tap Name and type giffgaff, then tap OK.
Tap APN and type giffgaff.com then tap OK.
Tap MMSC and type http://mmsc-ac.mms.o2.co.uk:10021/mmsc
Tap MMS proxy and type 126.96.36.199
Tap MMS port and type 8080
Now press the Menu button on your phone again, and choose Save.
Tap the little circle to the right of the profile named giffgaff on the list. It should turn green.
Your phone is now set up for giffgaff's internet and MMS settings.
Here is the shortlink to this guide: http://bit.ly/ggjellybean
Or download and run the Tweakker ICS APN Beta app from Google play using wifi.https://play.google.com/store/apps/details?id=com.tweakker&hl=en