We have same size house, bungalow, got it done 16 months ago, cost was €2,200 i think. This included all prep work and paint, 11 buckets of it, all white. Great job, saved us so much time. It was 4 months after by the time our house was fully complete, so with so many tradesmen onsite after walls are painted, lots of marks on walls in some areas, you will need to to a final coat in each room if you want to change the colour, or at least touch up with more white if you're happy to leave some walls white for a while.