Rebuilds using new parts, referred to as Watchco watches as they used to do them should be no more than £3k max for the date version 166.024, perhaps a few hundred extra if a decent bracelet is included. The date rebuilds were always prone to issues with the crown.
The 165.024 rebuilds (no date) were always more popular and they are probably around £3.5k these days.
Of course originals of both are at least double in price, if not more. I have owned three rebuilds and one original over the years.