I saw it fly out of the grass into a nearby hawthorn. I told my dad that I suspected I'd just seen a Wryneck and shortly after he confirmed it when he got a brief view of the bird sat on a branch. After a short wait it came into the open and sat there, allowing a more prolonged view than the bird a few days ago! We last saw the Wryneck head back into the middle of the Hawthorn.
After looking through my photos I'm pretty sure it's two different birds we've seen recently, and perhaps the bird reported on the Snook after we left was the same as the bird I saw on the 20th...
Here's the list of the other migrants we saw today...
2 Pied Flycatcher
6 Whinchat - including four together at Snook House.
c.6 Willow Warbler