Site insurance to normal buildings insurance?

[PI build]

We would quite like to move into our house to avoid yet another winter in the yurt in our back garden. The dilemma we have is that the house is not finished (watertight with first fix electrics and unplastered walls etc). Currently we have site insurance but that will become invalid if we move in. Are there any requirements on finish before you can have normal buildings insurance? eg. does it have to have a kitchen & bathroom or is living in it enough? Our house is officially a renovation of a 1930's bungalow but as it eventually ended up with only 1.5 tiny bits of original wall left it is almost a new build. So is the year of construction 1930 or 2021 for insurance purposes?