Overnight Parking in lay by's

Seen so many discussions on overnight parking and so many answers to the legality of such an act I did a bit of research and came up with this paper from the house of commons.  http://hansard.millbanksystems.com/commons/1984/jun/26/parking-of-caravans-on-lay-bys

 I assume it is still up to date (no doubt I will be told if it is not). I suppose if it is it would be wort taking a copy with you to keep on the van.I don't have any great desire to sleep in lay by's, but it is nice to know the law in case you get caught out on a long journey.