Depends on whether you know they are pirate DVD's when you purchase them. If you purchased them in a shop which sold normall DVD's and they looked genuine then I don't think you would get in trouble.
However, if you purchased one from those blokes who hang round on street corners selling obvisouly pirate DVD's then you could get in trouble.
Having said that I think you would be unlikely to be taken to court or anything. The handling stolen goods laws are there to stop large scale crime not the odd person buying something that may or may not be genuine.