Thanks for all the advice, roughly how much would the taxi be between the stadium and the airport in Madrid?
There are some taxi drivers in Madrid scamming tourists, but not too many.
During the day, about €20-25 total, at night about 30-35 (they will add 5 to the meter price for having picked you up from the airport - but there is NO EXTRA CHARGE for luggage). If it is more than this, INSIST that they give you a receipt "recibo" and check they haven't tried to trash the hole-punched serial number in the top right corner (like they did to my mates parents who were charged 55!!!!) and then let me know - we'll get them traced and get a refund. If they refuse to give you a receipt, throw €30 at them and tell them "Cabron!" (Son of a B/Big goat (stronger than it sounds)).
Also watch out for pickpockets on the metro, especially anyone with a coat/jumper draped over their arm. I am always on the look out for these people, but some old guy doing this took some worthless stuff out of one of my pockets on the way back into town from the Atlético game, which I found on the floor of the metro a few stops down the line.
Apart from these scams, there is very little violent crime in Madrid at least - and no-one is going to try anything on with LFC fans (who they STILL think have a hooligan reputation if provoked, despite our angelic behaviour at the Atlético game.)