On the subject of basil, sowing from seed has always worked perfectly well for me. I'd never buy a plant from a supermarket, I must confess. If you use a lot, sow several pots (never tried growing it other than in the conservatory). Don't know about over-winter - for the first time ever, I've just brought mine inside. With a N & E facing house, I suspect it may not get enough light to be really happy on the E facing windowsill, but we'll see.