You could contact the previous owner shown on registration document they may have forgot to leave the key in the car, or secreted it somewhere and forgot to tell you where. Some cars have a small elogated well about 50mm x 75-100mm long and 25mm deep which is where the chassis number is stamped, my Sierra had one an that's where I kept the key.
Have a search in every spot behind removable panels, in areas under the bonnet it could be placed, you'll be supprised where people put wheel nut lock key and ignition keys.
Alternatively if you know someone in AA,RAC or other breakdown service ask them if they would phone up their help desk and ask where you can get them taken off. Obviously you will have to prove to the garage it's your car, so take all documentation and a utility bill to prove the address. You might not need any but it's better to have it with you than having to go back. Sorry I can't help any further. Mine I knocked off with a cold chisel and club hammer but that was only one that had the key points knackered and the key wouldn't undo it.
Bob
bob
October 2005