At least double that. Optimistically. Then you have to take into account that the UK actually has no capacity to build yachts of the type. To have one built in the UK could balloon costs into the realm of the unacceptable while the ship could be less than desirable.

The yacht Samar is an example of a less than successful British attempt at yacht building. It looks like a ship you'd like to have. But it has more operational issues than a seventies Jag.