Your clued up on this stuff it is useful for certain medical conditions Parkinson's deseas etc plus other ailments....All the modern Cannabis strains are hybrids from the same 7 original heirloom/landrace strains that all originate from parts of Asia. Cannabis does obviously grow in other parts of the world such as Africa and South America but strains like Swazi Gold and Mexican Sativa and Colombian Gold did not really get mixed in till a bit later. Skunk no1 is a mix of Mexican and Colombian Sativa's and Afghani which is an Indica (i think)
The whole growing in a loft thing, unless you actually box it off and set it up properly i would never personally suggest growing in a loft, i mean why would you want to lugging big bags of compost up into the loft that's before you even get to the watering especially if you are doing a hydroponic setup. I hav'nt grown anything for a few years now but even when i did there is stuff you can buy (not cheap mind) that you put around the lights and if you have a proper air flow setup you can disperse the heat so the choppers don't see sod all. Still get the grow kit's also, don't forget the hydroponic stuff is designed for for growing fruit and veg and even normal flowers, It's great for growing massive ornamental flowers.
The debate for social usage will carry on ...,...
If you are caught growing it expect the law to come down on you in a big way .....