SXB and F3G you both raise very interesting points!
One thing I do not understand though, is why would a EU citizen need a residence permit in another EU country? Schengen or not Schengen....I definitely do not have and do not need a residence permit to stay in the UK
My Italian ID card was enough to let me in the country, and let me live here for the last 4 years! And if we (my BA fleet) didn't fly to some countries such as Algeria, the US and the Caribbeans
technically I wouldn't even need a passport to do my job! My ID card would be enough. Of course there's always the chance you end up landing somewhere else and that's why I carry my (Italian) passport with me at all times.
And SXB I understand what you mean about difficulties to live without a proper ID document in a foreign country.
Unfortunately the UK doesn't have proper ID cards which would have made life so much easier for me at the beginning. To open my first bank account or even to be registered with the NHS they asked for my Italian passport and a gas/phone bill as proof of address....not easy when you've just moved and are renting a room somewhere because you can't afford anything else!