What a great morning out playing in the snow. Thanks to Andrew for the suggestion and to Grahame for the navigation.
As Grahame said earlier, this loop is do-able on a cross bike, which is just as well, cos that's what I was on. Not sure whether it was a help or a hinderance really - the narrow tyres seemed to cut through the snow and mud OK, but I found the icy road sections pretty dodgy, and I was a bit overgeared in places.
Also had a couple of
NO BRAKES moments, when I discovered that a layer of compacted ice had formed between the brake pads and the rim - Hal almost got my front wheel parked somewhere where it shouldn't have been parked as a result of one of those moments.
I bailed out before the end because I had to get back for an opticians appointment, so missed out on tea chez Grahame.