Your cars MOT will have been due on the 3 year anniversay it was first registered. So although it is a 56 reg, it could have been registered between September 2006 and end of February 2007. Look at the documents and see when it was first registered. It will be due between Sept 2009 and Feb 2010...
I don't know if there is a time limit, but you could try getting advice from your local citizens advice bureau, or ring a solicitor, some have a 15 minute free consultation. Or you could try the Criminal Injuries Compensation Board (if you are in UK). I'll try and put a link on