UK Car Repair Questions? Ask a Mechanic for Answers ASAP
I am sorry that you have not been helped yet. I just came online and saw your question.
Although you see some water dripping out from the ac drain, it sounds like it is partially restricted and most of the water is backing up and coming out onto the floorboard. I would use compressed air to blow out the drain tube and then a shop vac to suck out all loosened debris from the compressed air being blown in the tube.