Spent ages trying to locate the source of the oil on top of the front diff.... any thoughts? Will get the car on axel stands later this week to have proper look.

Click image to enlarge

Two possibilities that spring to mind...

There's a breather on the top of the front diff which is a rubber hose pushed onto a spigot that sticks out of the top of the diff. Make sure that's attached properly.

The only other thing I can think of is the NS valve cover gasket is leaking.

Hopefully it's the breather as doing the valve cover gasket involves removing the supercharger so it's not a 5 minute job to sort out.

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior