I was trying to replace a flat tyre and seems not to be able to remove the relevant wheel nuts.I guess I couldnt remove the nuts because of the same thing tha appears to have locked the steering wheel. Cant start the car either as the ignition key wont turn. I supect it may be a safety measure but I am getting desperate and relatively close to calling the AA. please help.........

Try wiggling the wheel w the ignition key in the keyhole; see if that will unlock it.