It looks like I've enough bricks to build a small house, but it's surprising how many it takes to lay three or four courses beneath a path, as I found when I started to do that at the far North boundary. But I might need more. I need to see how it goes next year: if there are still water-logging problems on the West bed, I'm going to put in another deep, though narrow, path along there, and another going across the bed, and the most water-logged part, and thence into the pond. I've got a long (20ft?) section of pipe which I could put holes into and run under the path, straight to the pond.
Not that I'm obsessing about the allotment, water-logging, and drainage or anything... But I needed to get that off my chest before I begin EdD work for the day. In respect of which, btw, there's been something of a eureka moment in the last 24 hours.