Bonjour Ian !
Mmmmmhhh, I checked to make sure that my first instinct was correct, and indeed, Merseyside is masculine in French:
See https://fr.wikipedia.org/wiki/Merseyside
This got me wondering whether all English counties are actually considered as masculine in French (regardless of their ending), so I went around to check.
It turns out that Merseyside seems to be the only -e county (except for the -shire ones), and all are masculine, with two notable exceptions:
- Cornwall, which in French is translated as la or les Cornouailles.
- Isle of Wight, which is a special case due to the term "île" : l'île de Wight.
J'habite (sur) l'île de Wight.
Thanks to you, I learned something today :)
I hope that's helpful to you too!
Bonne journée !