my '94 WRX i had about 13 years ago came up as a 1.8GL too - i put it down to someone in the DVLA making an error or previous owner being fly. The logbook stated what the car was correctly though so was just a matter of explaining to insurance company the correct model and going from there. Would've been nice to have only paid the premium for the 1.8GL but it's best to be legal!!!