Agreed EV is the key Lets say 250 for 25% Net Debt drops to 350...

Agreed EV is the key
Lets say 250 for 25%
Net Debt drops to 350
Remainder of asset drops to 750 million
Therefore EV is now 400
Add 100 million for all other assets ( this is flexible based on current U price I am discounting heavily )
That's 500 million i intrinsic value from an asset perspective

I would expect though the additional breathing room and the fact that the deal derisks PDN and ensures it will be viable for many years , there will be a premium based on its value reflecting the likely higher future U price and cash flow .
I would expect it to trade at an EV / market cap of about 600 million with the future value determined by the U price

Interestingly the sale price , whether 25% is sold for 200, 250 or 300 m will have a big impact on the rerating as it impacts the market value of the remaining 75%