http://www.dailymail.co.uk/news/article-2544536/AA-refused-help-mother-accidentally-locked-toddler-car-took-150-membership.html
The police or the fire service will generally help out in situations such as this.
I have twice locked myself out of a car, the first time was when there wasn't so many dishonest people around, because I simply went to a close by Halfords shop (who in those days held stocks of the most popular car keys) and for a deposit of just £1 they lent me a brown bag full of keys, I then sat on the kerb edge trying out these keys until I finally found one that fitted.
On the second occasion i was near to a police station and I went in to explain what had happened and they sent out a policeman complete with a certain tool and he simply pushed this down the door jamb and lifted the latch.
Ah those Halcyon days of yore.