I found out what the problem was. The phone was bought second hand and it turns out that it was barred. All is well though as I got a different new s4, and it was nothing to do with 48 at all. The reason I thought it worked with the Vodafone sim was because the data roaming came on but in the end it didn't actually function properly as service was still not available. Thank you for your help on this, it was appreciated even though there was nothing that could be done to help in the end.