I was in the same position with my Dad's army records. He too was in the RASC and his records said that he landed in Normandy on the 7th July, well after the main invasion. He was with 94 Bulk Petrol Transport Company RASC and I don't think that you would want to be landing their bowsers in the middle of a fire-fight.
To find out more, I got hold of the war diaries for his unit and they revealed an awful lot of detail, some of it rather mundane and repetitive but otherwise there was some really interesting stuff. Not being able to get to the National Archives I hired a researcher (recommended by someone else on this forum) who photographed the sections of the diaries I wanted and sent them as jpegs. I was dreading the cost but was pleasantly surprised and am really glad I did it. If you like I can pass his details on to you via a PM.
Jack
