Update your number

1. Go to Settings > Phone > My Number
2. Replace the temporary number you find there with your own number - use +44 instead of the first 0
3. Then tap Save

Reset iMessage settings

Your iMessage settings won't reset themselves during porting - the temporary number will still be in your new iPad.

To input your old number into your new iPad:

1. Go to Settings
2. Tap on Messages
3. Tap iMessage ON
4. Scroll down to Send & Receive number
5. Replace the temporary number with your old number
6. Then tap Save

That's it, you're all ready for action.