How do I bathroom / kitchen / extension? etc.

overall build floor area - 4.6m wide x 3.5 deep = 16m2
16 x £3000 say for building work and materials = £48,300

• kitchen, finishes, joinery and appliances = 25k say so £73,300.
  Structural engineer, architect, building regs 10k say = 83,300
  VAT £16,660
  Total : £99,960