I picked some more shaggy ink cap mushrooms from the field at the end of the road. I also found three other types of mushroom, but I could only identify one.
The one I'm pretty sure of is a Little Japanese Umbrella (shown top left). It's supposed to be edible but they're so titchy it's hardly worth the bother. They're also really pretty (my blurry photo doesn't do it justice) so I'm happy just to admire them where they are.
I also saw lots of these little white mushrooms (centre right). They were perhaps a couple of inches across, pure white caps and gills, the gills running down the stem like a chanterelle. Again, my photo is poor - the gills are quite widely spaced and they fork. Some of the caps had a smooth round edge but some had a "toothed" appearance where the cap had begun to decay leaving the gills sticking out. Since I didn't know what they were I left them alone.
The last type of mushroom I saw (bottom left) might have been almost any type of large brown mushroom. They were so degraded it was hard to tell. They were the largest mushrooms I saw, about four inches across. There were a fair few of these, and they must have been pretty substantial before they started to rot away. So if they are edible they'd be very worthwhile to collect.
It's not very satisfactory standing in a field trying to flick through a large book comparing pictures without any clue how to narrow down the options. A few times I thought I had a candidate only to learn that the type of mushroom pictured only occurs in birch forests in the spring, not in fields in the autumn. Or a picture that looked very similar in the book turned out to be a super-magnified close-up of a mushroom that is millimetres across, not a few inches like the mushroom I am looking at.
So if any more knowledgeable readers can suggest what these mushrooms might be, if I spot them again I'll try to compare them to that suggestion. I know you can't identify mushrooms by a picture only, so I won't do anything stupid like eat them just on the basis of some stranger on the internet saying "They look like chicken-of-the-woods to me". But it would give me a point to start. At the moment I am floundering.