Not surprised at the extra charge ~ it's 'cos they have to pay to dispose of it I expect whereas the theory is a householder can either take it to the tip or pay their local council to pick it up. But you would know that anyway. 
The mattress is usually the heaviest part of the bed but I 'spose you have underbed drawers that are stuffed with a lifetimes accumulation of crap.
Nevertheless I have yet to meet a double (or larger) divan bed where the base didn't split into two halves for ease of removal ~ or for that matter a carpet fitter and mate who aren't susceptible to fluttered eyelashes and a proffered tenner tip for moving those items that "Poor lil ol' me jest cain't manage on may own y'all"
The bed is currently a big heavy wooden one and would need dismantling to move out
....really can't be arsed with that. The mattress is new , hugely thick and extremely heavy so I will struggle with that on my own.
The 4 draws underneath are are packed to the heavens with 'stuff' ...
I want to get a new iron bedframe thing but that will have to wait for the sales - I have seen the one I want - target is locked on and justification are now being provided to myself to spend the money. It is inevitable . It will be mine
