I am not sure if its the right thing to diverge a fair bit from the original topic of this thread, but as underexposure is the key subject I shall give this a go one last time.
Maybe your client genuinely asked you to display the space as dark and grim; if so fair enough. I got like 2 or 3 of them over the years.... all the rest hate dark images like plague. These are clearly then not portfolio or example shots. Submit, delete and forget. Instead let's see shining examples if you wish to share. I feel like this was all just baiting to see if we give these a pass.
In general, It is in fact quite acceptable and much preferable to blow some highlights in the lights and even an odd window, particularly if the view outside is truly rubbish, to save the rest of exposure if for whatever reason it can't be perfectly controlled. It won't look super great in more extreme cases but it will be a pass. The point is the general public likely won't notice much difference, and certainly don't expect bright halogen to be 250,250,240 light golden instead of simple pure 255,255,255 white (problem starts when it becomes 230,230,230 grey which is impossible - i see this all the time). In US, the views, and particularly proper views need to be nice and clear; the UK is a fair bit behind the curve.
In the 2nd post there are some obviously badly done shadows in the 2 follow up corridor shots. It's admittedly nowhere near as extreme as the exhibit A, but still similarly underexposed. Besides I bet you there is something really dodgy going on with white balance in the last exhibit due to mixed lights (cool window on the right? and the warm tungsten our fluorescent). Technically, the camera may be seeing it this way, but this is not how anyone walking and talking under the sun would perceive such a scene. You simply can't win if you let them mix as is, but with appropriate exposure it would at least look 10 times softer and then you can do some trickery in photoshop to make it better, but really this should be dealt with before taking the shot. There are many different ways I could think of.
I don't know why it was necessary to show so much ceiling, particularly with that massive lens artefact at the top. Crop it out, step back and zoom in, change height, etc. Nobody cares about so much ceiling - that is the point. Making it look round is confusing at best for the general public.
Bathroom shot is not too exciting and nothing too major or very difficult is going on. The mirror is rather odd, but certainly the toilet seat is missing something extremely important (an odd cost saving measure? or just broken off?). Certainly not one to keep as an example, particularly for US clients.