BMW 523i Overheating leaking antifreeze and driven for 5 mins

Hi I had a mechanic change the fuel sensors of my car and when he was driving it back to me he said that the car overheated the temperature gauge went into the red and he was on a A road with no hard shoulder. He had to drive it for 5 mins like this before he could safely pull over. A friend towed him back to his garage and he said that there was antifreeze leaking everywhere. The car is R reg but has only done 76K miles I am quite worried about the damage and whether or not driving it whilst the temperature gauge was in the red for 5 mins might have blown the head gasket. Can anyone help please and give me some suggestions as to what might have gone wrong and costs to fix it?