You seem to be using an iPhone so you'll almost certainly have to put a small amount of cash credit on your account to pay for UK SMS messages that it will try to send to a UK server in order to activate the phone, FaceTime, iMessage etc.
Try putting €1 cash credit on your account then switch the phone off and on again wait a little while and see if it activates and you get a network connection.
Unfortunately this is the stupid process that Apple insist on using.
Hope this helps.
