Safe laybys

Hi all, I need some advice please. We are traveling down to Norfolk this weekend and notice that our usual route which includes the dreaded Holdingham roundabout on the A17 is closed in both directions.we have decided to go via Peterborough picking up the A47 which seems a decent route . We plan to stay in a layby but don't really know if there are plenty between Peterborough and kings lynn . I know they are usually awash with lorries and someone on another site has thrown the beware of lots of travellers which I didn't even give a thought to . Is there any decent laybys on this route or should I wait till I'm well past kings lynn to stay the rest of the night.