What a relief that your DGS's illness was not more serious and he is better now.
Yes, I most emphatically do the think the surgery should have reacted positively.
I think the problem was a badly trained receptionist, who did not fully understand how serious the emergency was. If you had managed to speak to one of the doctors, I am sure he would have reacted positively.
I would write to this surgery describing the events and ask them, if they really do not treat anyone, even in a dire emergency like yours,unless they are a patient of the surgery. and what about a car accident outside the surgery door. If you do not get a sufficient reply. complain to the health authority.
Many years ago DH was taken ill when away on business. He staggered into the nearest surgery. The receptionist refused to let him see the doctor until he had made an appointment and none were available for that day. At which point his legs gave way beneath him and he crashed to the ground. He was seen within seconds.