You must have led a sheltered life, it's not that small. The footprint is about 8m x 5, 2 floors, so 80 sq m overall. That's adequate for a 3 bedroom home. I've lived in a smaller 2 bed place, that was just shy of 50 sq m. Where they have fouled up the design is in insisting on having multiple bathrooms and lavatories, as is the modern way and as the market expects. This eats living space because you don't live in the bathroom.
As for the price, it's in Oxford. There are few more expensive places in the UK.
You're right about the overall size, but the layout is terrible and makes very poor use of the space (or lack of it)... this is where UK builds are so poor... total lack of thought and innovation... yes changing it to something better might cost a little bit more, but so worth it.