Weather forecast notwithstanding I took the dogs to the plot yesterday and between showers dug a spade-wide trench down part of the Western boundary, and then across the NW bed to the central path where it should flow down into the pond. I had the pleasing sight of it actually working, the trench filling with water, which followed me as I dug in the direction of the pond.
Gorse, apparently, doesn't like wet, boggy ground. It's planned to be the staple plant of the hedgerow at the central area of the Western boundary, so the drainage needs to work well if it's going to thrive. It might be that along this section of the hedgerow, I'll need to plant pyracantha. I've bought 100 seeds, but have a feeling in my bones that it's going to become the mainstay, and I'll likely want more.