Rural English roads can get a bit muddy during the winter.
I do love English understatement.
Actually, it is in conditions like those that the big, clanking, vulnerable, difficult to fit, Dutch chain case has a slight temporary advantage, in that the infill between the top and bottom chain runs stops the rear wheel depositing dirt on a prominently visible part of the bike, as it does on the lower run of a Chainglider. Of course, properly cleaning the back of a Dutch chain case is hellishly difficult without disassembling the whole thing... Six of one and half a dozen of the other, and I don't even want to think of cleaning all those inside corners of a Gates belt drive after riding where you do.
A mudflap on the front mudguard may help keep the muck off your crank and legs/trousers. See the discussion passim on this forum.