So what’s the correct way to pipe up a Fuel Pressure Regulator on a Renault 5/9/11 Turbo model fitted with a Solex Carburettor??

The details are in the Haynes Manual from many years ago:

But to make it super clear in-case you were searching for this:
A: Vacuum Line to Carburettor
B: Fuel Return to Tank
C: (Smaller Diameter) Fuel Feed to Carburettor
D: Fuel Feed to Engine from Fuel Tank/Pump

The details are in the Haynes Manual from many years ago:

But to make it super clear in-case you were searching for this:
A: Vacuum Line to Carburettor
B: Fuel Return to Tank
C: (Smaller Diameter) Fuel Feed to Carburettor
D: Fuel Feed to Engine from Fuel Tank/Pump