well its not exactly totally blocked.... what you do is you carefully put one leg over the pipes then the other whilst carrying your tools...most timber floor houses have pipes running everywhere underneath them at grade so they drain the waste water or stormwater away to a main drain meaning you have to crawl under or over them at some point.

Looks ok to me, you even got steel strapping to hold it all up. I see far worse every week....every single week...

If all you are withholding 50% of the money over is this,and the other "issues" you have identified with photos your fighting a losing battle.

But what would I know, im only a qualified plumber,gasfitter,drainlayer..............