The GP is def the best way to go, unless you have faith in your loca ED - mine i was taken in by ambulance, my friend followed with DD (only a couple of weeks old) and i sat in pain in a wheelchair in the waiting room for nearly 3hrs with a nearly new baby and no bra only to get in, be checked over and finally at 10pm at night told they couldn't do anything they suspect it's gallstones but to go to my GP, get an ultrasound and go from there.
I could have gone to my GP and had an ultrasound by 5pm that day if i had of skipped out on the hospital.
I was on the waiting list for a couple of months, i had it out when DD was about 5mths old so possibly a 3-4mth wait down here.