I have just done a bathroom for about £6k.
It involved taking a wall down, moving a door replacing a window. The bathroom was completely re plumbed and rewired.
The labour and plumbing components was £3.5k. I spent about £2.5k on suite, lights, and tiles etc.
I shopped around and bought good quality “branded” stuff, if I had paid full price for the taps, shower, cubicle etc, it would of cost me about £4k for the big stuff.
There are big savings to be made but you have to be willing to take a chance and spend time looking around. e.g. Shower cubicle brand new off ebay for £150, the same cubicle for sale on-line for around £400. Taps can be eye watering expensive!