Not sure if this is still true but Royal Mail used to give discounts on bulk posting if items were sorted in Postcode or Walksort order, so maybe that's how they were sent out.
Got mine last week. But as usual found it difficult ot navigate through. The directions given to sites are, I think rather confusing. The Caravan Club way of giving directions is better. ( Or is it just me???)
------------- It's not what you take when you leave this world behind, it's what you leave behind when you're gone