Rush of blood to the head

You guys must realise that I am not the most impulsive of people in the world but today I think I must have had a bang on the head without realising (-;
I've been saying for weeks now that we need a new car so off we went today to 'have a look' at the Peugeot 307 and the new shape Astra. To cut a short story even shorter, 1 test drive and 60 minutes later we walked out of the Peugeot showroom having put down a deposit on a 2-year-old 307! I was a couple of miles down the road before I realised what'd happened.