Thanks jas,
I have done only 1 short Nav so far which was less than 30 minutes to the destination so I suppose DR navigation was suitable then, and my instructor was also reading the Garmin 430 so I suppose if he is doing that then on our Navs we are legal. I was just wondering if using DR alone was a suitable method but it appears not to be.
Or maybe it is if you have a "full time flight navigator"?