imessage mobile number ipad 4 ios 6.0.1

Dear all,

I am having a little bit of trouble and so far despite searching and searching I can not find an answer or resolution that works

I have recently got the iPad retina display (iPad 4) on mobile data (cellular) with T-Mobile UK 3G (aka EE, everything everywhere) and wi-fi.

I have one iTunes account and ONLY this device - onle ONE device which is synced using iCloud only.

I put the sim in and set everything up

However in Facetime & iMessage I did see the mobile number showing - on software 6.0.1

However since updating there and then to 6.1.1 the mobile number is NOT showing in Facetime and iMessage but instead my email address used for apple id greyed out

I can add new email but no mobile number - and even when I type my mobile number it obviously comes up with error with email or something to that effect.

I have reset to factory settings, tried signing in and out of apple ID both within the facetime and imessage settings as well as iCloud, itunes and store

The mobile number is also registered to my apple id correctly

But still my number is not being picked up as a point of contact as well as the apple id email address.

So I have the following questions:

1. Is it possible to add the designated mobile number from the sim card to iMessage and Facetime as well as the email address greyed out?

2. If yes to question 1 - how bearing in mind the above steps I have taken to resolve the issue which have not resolved the issue?

3. If no to question 1 - why not? as iphones on the same ios software uses a mobile number a point of contact in facetime and imessage

Thanks in advance everyone