when do you qualify for NHS?

Except in UKBA terminology a 'spousal visa' is also called a 'Settlement visa'. Semantics I know but they're not mine. Don't shoot the messenger.

Like I've said before, we have often had people refused to be registered based upon their visa status be it spousal, finace/e or work visas. Heck I know of at least one who was overstaying a VISITOR VISA BY 4 YEARS that got registered. It seems to be at the whim and interpretation of the GP.

I think you are right about the interpretation - my wife registered at my GP with no problem and at another (purely because it was taking too long for the acknowledgement of acceptance to come from mine - and it did later), neither of them even looked at her visa, they just accepted her.