I'm having a bathroom renovation nightmare too. It isn't even the whole bathroom we're doing - just a small shower area.
Not knowing anything about plumbing, we went to a place which was recommended to us, expecting them to look at our room, sell us what we needed and fit it. The first thing that happened was their fitter pulled the plug on the job the day before they were due to start in November because another job had over-run and he didn't want to let the customers after us down. So we found our own fitter who arrived to start the job yesterday.
He took one look at the stuff we had delivered yesterday and said that the shower tray (which was acrylic and had 16 plastic feet to hold it up) would cause us problems down the line and we would be better having a stone resin one on a proper plinth. He also realised that the concealed shower we had chosen wouldn't fit because the cavity wall wasn't deep enough and there was a supporting strut in the way. It seems either the original fitter guy who measured up didn't pay attention to the width of the wall or the guys in the showroom didn't pay enough attention to the measurements when helping us select a shower.
So now the project's been delayed again because we need to order a different tray and shower. To make matters worse, the wife upset the fitter this morning and he nearly walked off the job. He's asked me to pay him for the stripping out work he did yesterday so I wouldn't be surprised if he doesn't show up to finish the job when the replacement stuff arrives.