The first floor of the Prime Minister's House is open to guided tours on Monday, Wednesday, and Friday. The second floor is not open to the public and is only accessible to the Prime Minister, their family, staff members, or people that they personally invite.
The first floor's design plans are officially to remain unchanged as Prime Ministers change, but in practice, things such as hanging new paintings up, rearranging furniture in the PM's office, and adding small objects to give it a bit of a personal touch is an accepted practice for each new Prime Minister. Conversely, the second floor is dramatically altered for each new Prime Minister and their family, in order to make it feel like home for them.