Hi Tom, the locking wheel nut key in the set you purchased is only suitable for the locking nuts in that particular set. It is highly unlikely that the same key would fit the wheel nuts on your own car unfortunately (there are a total of 26 combinations).
Just like the key for a car, they are all cut in a unique way so that you can't just use any key from any random set to remove the nuts. Anything otherwise would be a security risk.
If you have lost your original locking wheel key and need the locking wheel nuts removing then we offer a removal service free of charge using our Master set for any previous customer at our warehouse in Ilkeston, Derbyshire. Please get in touch if you would like us to help. Thank you