Rod, don't worry about your perceived ignorance, no one here knows everything and I'm certain there'll be guys who'll chime in to this thread with far more info than I could offer. As for different aircraft types and the use of spinners, each aeroplane was different and as far as I know there was no set cowl type; it was more the application on the aircraft owing to various reasons, either streamlining or not, or improved cooling or not. I guess the Lanc II needed spinners more than the Halifax III, why I couldn't say, but it might be that the Lanc was faster than the Halifax. Halifaxes initially suffered from being underpowered and overweight, although this was a concern for the Merlin engined variants, so the absense of spinners on Hercules variants might have been as a weight saving measure.
As for Beaufighters, I think the spinners were removed because they didn't need them. I think later TF.Xs might have had them refitted, I suspect, for streamlining.