A strange and sorry situation to be in. There are some employment forums on the internet, go to them they might be able to help you out.
Go to your local employment helpline or employment tribunal for further procedures
http://www.employmenttribunals.gov.uk/
Why did u leave the office?
Why didnt you call up the MD right then and there?
What about the other person whom you were talking to? Can't he or she give any evidence?
What ever the case, do not go in the meeting alone, take someone with you, and if possible take a mini recorder with you and take notes as well.
If you are telling truth and nothing but the truth then there is something fishy going in there.
Good Luck