Autodesk have created a very ruinous outcome for many multi platform users in the UK by introducing an Internal Origin that the Project Base Point cannot be Clipped or Pinned to whilst having geolocated Ordnance Survey coordinates applied to it. This was not the case for all previous Revit versions including Revit 2020.1
There is a solution that I used today and in the past, that retains Project Base Point at Internal Origin, but crucially allows the Ordnance Survey Coordinates in millimetres to be applied to it.
1) Open Revit 2019 or earlier
2) Create a new Revit project using any template .RTE
3) In a 3D view turn on the visibility of Site>Project Base Point and Site>Survey Point (Internal Origin is absent)
4) Select the Project Base Point and enter N/S: 155550000.0 and W/E: 484100000.0(mm)
5) Zoom All, select the Survey Point, Unclip it and Move it using Snap Point(SX) to the Project Base Point
6) Re-clip the Survey Point at the Project Base Point (which is at the old 'invisble' Startup Location/Origin)
7) Now Save this Revit file using a name like "Project Coordinates" and Close it
😎 In Revit 202.2 or later open the new Revit Project or Create one
9) Open a default 3D View and turn on the Visibility of Site>Project Base Point and Site>Survey Point
10) From Insert>Link Revit browse to the "Project Coordinates" file you just created
11) Set Positioning to be Auto - Project Base Point to Project Base Point
12) Go to Manage>Coordinates>Acquire Coordinates and point where the Project Base Point is to select the Link
13) Your Revit 2020.2 or later Project Base Point remains at the Internal Origin but does not move from it
14) Zoom All, select the Survey Point, Unclip it and Move it using Snap Point(SX) to the Project Base Point
15) Save your Revit project
The outcome of this is that IFC / NWC Exports will have your 3D model geometry positioned relative to the UK (or other) coordinate grid system intersection and the Revit Origin. This removes all of the issues people are having when federating models in Navisworks and effectively reinstates the model set up process required in the UK for many years now.
Please leave feedback on the success of this, and if there is a way to achieve the same outcome without using earlier version of Revit.