Exactly what happened with me too! Except there were a couple of minor things I didn't manage to pick up after they 'amended' the drawings and they got transferred to my construction drawings.
Come building time, PD moves SO quickly you don't even get a chance to blink and BAMM! the mistake from the construction drawings become a reality. SS will not budge because you've signed a 'contract'.
I have been put in that EXACT same position too. PD choses to overwrite whatever they want in the contract.. like for example.. my staircase detail plan clearly shows glass balustrades all the way to the top of the stairs.
http://i1327.photobucket.com/albums/u67 ... 17455c.png
But when the stairs were built, they just added a dwarf wall to the top of the staircase. Their argument was "Oh the mistake was made by the draftsperson in the Staircase detail plan and all Waldorf staircases comes with a dwarf wall on the top of the stairs due to the stairs extending over the fridge space, as shown on the construction floor plan, which is the correct one, so we are going to ignore the staircase detail plan because we are saying it is wrong" (which I have attached and highlighted the area in question)
http://i1327.photobucket.com/albums/u67 ... 6ee1b5.png
So now its going to cost me $$$$$ (and quite a lot of it) just to have the stairs redesigned and rebuilt to have the glass all the way to the top. I can't help but wonder, if they just want to blame me for signing a plan that is EXTREMELY hard to notice one small detail there and pass the costs on to repair their mistake to me. I argued that the detailed staircase plan should over-ride that floorplan but they refuse to concede.. bottom line... PD seems to just pick and chose whatever is in their favour when it comes to a mistake in the plans.... so I am left with no choice but to fork out more $$$.
Was it in your contract to do glass all the way to the top, or not do glass all the way to the top? If it wasn't in specifically written that it was or wasn't in the written contract the next legal document is the plans. Usually more detailed plans overrule. The other issue is that they would have recieved council building permits based on the submited plans, now they are changing those because they made a mistake. Have a chat to your solicitor about what options you have.. Potentially holding out on your final payment until they fix it.....
The only spot I can see from both plans is that there should be plaster at the top of the stair case blocking the view into the master bedroom from the void, but not NEXT to the stair case. It is even more clear from the way the arrow only points to the one wall. Is that what you were expecting?