If I see it correctly, PGC, as far as Great Britain is concerned, uses as third level administrative units ("counties") the current Council Areas in Scotland/Alba, the current Principal Areas in Wales/Cymru and the ceremonial counties in England. This is fine.
However, apparently the unitary authority of Warrington is considered part of the ceremonial county of Merseyside on PGC. If I understand it correctly, this is a mistake, as Warrington U.A. is part of the ceremonial county of Cheshire, as far as I can see, e.g.: https://en.wikipedia.org/wiki/Subdivisions_of_England
Unless British colleagues with a specialisation on British administrative geography have a different view, I would ask to correct this mistake.