When you already have fixed windows, it becomes a custom application because standard OEM Rover windows don't fit in the hole left when a fixed window is removed.
This requires a custom window the same size or larger, but NOT smaller like the Bearmach or Britpart ones.
You have to fill the hole left when the fixed window is removed.
The custom ones from Motion windows are the only ones that I have found to order that will work.
Years ago I had 4 Series sliding panels cut up and re-welded to form 2 double sliding roof sides.
The result was nice, but the almost all windows like this one will be.
If you had solid panels, well that is a blank canvas for whatever you want to fit.
Uncle "Richard" Douglas has a Land Rover with big wheels that never gets stuck... until he breaks something so it won't go. Uncle Douglas always breaks something. - Anna Crowther at the Conclave 2012 (AKA Carburetor Neck)