My initial thought was to stick with the fairtrade/organic option, but a bit of research suggested that Silver Spoon might not be such a bad bet - they are Red Tractor certified, which means that although a long long way from organic, their farmers do adhere to minimum standards (e.g. not cropping for a set amount of time after spraying).
However, a quick look at the Farmers Weekly forum suggests that British Sugar (of which Silver Spoon is a member) is another corporate giant trying to push down prices as far as possible, and that lots of farmers are planting smaller/no sugar beet next year due to the crap price being paid by British Sugar. However, the farmers are able to make the decision to plant something else, unlike those in countries with few crop alternatives.
British sugar
Cons: Not organic (I can't find any source of organic British sugar), British Sugar is a crappy evil corporate monster, not willing to support British farmers if the price isn't at floor level, although farmers can grow an alternative crop if the demand isn't there.
Pros: Far far lower carbon emissions, money staying in local(ish) economy
Imported sugar
Cons: High carbon footprint, farmers more likely to be trapped into growing one crop by prices, lack of demand for alternatives, unsuitable soil etc etc.
Pros: Organic (if I choose, although it is monstrously expensive), fairtrade means that at least they are being paid a sensible price.
Really I need a British farmer to come on here and tell me what to do. Would they rather I spent my money with British Sugar, potentially encouraging them to pay farmers a crap price, or should I take my demand elsewhere, namely to imported sugar?