I have basil sown at the end of August on my window sill and whilst it germinated well it does not appear to have grown at all in the last month. Is this due to light levels? Did I leave it too late to sow this year?
Yes you were late! Basil responds to high ight levels and warmth by day and night so new growth in October is only from plants with existing strong roots (i.e. sown in spring or early summer) and leaf quality tends to decrease.
Maybe buy some plants from supermarket salad bags?