I think this is one of the worst situations for CA. Very high contrast edges with a narrower than usual spectrum. I'm still surprised you were struggling for shutter speed, the Scottish sun must be feebler than I remember. Try sitting down, bracing elbows on knees, press face to camera, shutter on exhale, and expose for the highlights. Even if you get shake on the first shot, if you take three or four (not with motordrive) one will often be usable.