my car is going into limp mode

my vw passat has a code coming up its for Wake-Up Line for Control Module Electrical Handbrake will this be a big expensive job as halfords wont do it and said it needs to go back to vw sometimes it drives perfect then as your driving along two warning lights come on together and the speed drops and it is limp when you turn of then on sometimes this works and it goes ok but not for long