Most courier/freight companies charge based on 'cubic weight' - that is they assign a weight value to a cubic size, so 1 cubic metre will cost x amount. Even if the 1 cubic metre box contains feathers, it will be charged the same as another box containing books for instance. But if the item weighs more than the cubic weight, the cost will be based upon the actual weight of the item.

So its best to be pretty accurate when quoting the items size.

It may be worth trying bus freight, however they may do the same thing or even have a maximum size - its worth remembering too that most courier/freight companies will have some kind of insurance should something go wrong - not sure thatthe bus companies would provide that.