John C
Not sure which version of the FCTM you've got.....but mine says LAND ASAP. The QRH Procedure, top of the page, LAND ASAP (RED).
If you've got uncontrollable smoke, it's "do or die". A Commander has the authority to deviate from SOP's, rules and regulations IF the aircraft, it's occupants or people/property on the ground are in Immediate danger. It could be argued that shooting an approach in marginal conditions increases the risk - but delaying possibly guarentees an accident (SR111?)
If you fly in Europe, we have a plethora of available airfields to land at - more remote areas may require use of the "AT ANY TIME" part of the QRH i.e. Ditch/forced landing.