Hi there, interesting discussion.
I have a kind of opposite problem, as I am a British national living in Italy but my kids are Italian citizens. When I came back to the UK for Easter the official at passport control in Stansted airport asked me to prove I was the mother of my daughter!! I couldn't obviously (and my kids are 11 and 9, we have been back to the Uk at least onece a year since they were born and I've never been asked for a birth certificate until now!!). He let us enter the country (I could understand his attitude more if we were trying to LEAVE the country, but we were entering the UK), but told me always to have a birth certificate on me.
Now I'm coming to the UK again for August and this time I'll be prepared. But I'll be returning to Italy alone and my kids are going to follow one week later with my parents (their granparents). Any ideas as to what I might need to let my mum take my kids out of the UK and bring them to Italy? I have documents allowing my mum to travelwith them from the police station/passport office here in Italy - but it's all written in Italian. I contacted the British Consulate in Milan and I got an automatic reply telling me to check teh website - very useful!!