the aa will just deliver u to a garage that will charge you to drain the tank, easiest way is to stick a jhose pipe down in to the tank suck with your mouth, and as the petrol is about to reach your mouth put the hose pipe in a large container big enough for all the fuel, do this until your tank is as empty as possible, and then fill right to the top with petrol,
thats basically what a garage will do exept not using the mechanics mouth, a pumping machine instead, another way would be to get the back of the car off the floor, and take the tank off, but am not sure how easy that is
hope that helps ya matey