There's actually a button in BLAM to do the first part of this.. 'Set line of sight scale pivot'.. but you can do it by hand.
Set the Pivot Center to the camera by ShiftS putting the 3D cursor there, and selecting '3D Cursor' as the Pivot Center.
Then, selecting all the objects whose dimensions you want to alter, (not including the camera,) with the counter-top active, uniformly scale (S) all the objects in your scene, until the right dimension appears in the Z of the counter-top. The size of the objects will not change in the (perspective) camera view.
You could also place an Empty at the camera, temporarily parent all the objects you want to scale to the Empty, and scale the Empty. This gives the opportunity for more accurate control.
Swipe and Ctrl C copy the Z dimension of the counter-top into your clipboard. Select the empty, swipe all its scale fields, and type the desired dimension into all of them, followed by / and Ctrl V ( your typed result would be '30/0.17759', if you wanted a 30mm thickness). Then Alt P , unparent the objects, keeping their transformations.
It's probably better to apply (Ctrl A) the scale of your objects when you're done, to put the new dimensions into the meshes, rather than their object transforms.
Please find the scaled file, with counter-top at about 35mm. Scaling did involve some steps I couldn't include in this answer without seeing the scene: adjusting clipping distances on the camera and in the view.. scaling the camera to make the view practical. The method described still applies, if you need to tweak.