I thought I saw so many possible connections with geographical features and ancient languages like Anglo Saxon, but you burst my bubble with your so logical answers. Well done, a truly diabolical grid, but one I might possibly have solved (if I was a genius) as none of these groups are actually outside my knowledge. You have my true respect.

Great. Knowing the Hen link, and spotting that line first really helped. Don't know how anyone growing up without Oor Wullie etc. would solve this wall. Having the Hat and Hoo groups in one wall was evil, but excellent. 10/10

Thank you!
The whole grid started with the 'Hen' line.