The United States (Hawaii) or the Republic of Kiribati.
The halfway point would be in the Pacific Ocean 500 miles NE of the Kiribati Islands and 1000 miles S of Hawaii.
(*The closest minimum distance is 7044 miles (11336 km) between Vancouver and Auckland.)
where is halfway between newcastle and london
Leeds is roughtly halfway between Edinburgh and London.
The distance between London, England, United Kingdom and Auckland, New Zealand is 11390 miles (18331 km).
It would be close to Greenland, just off its west coast.
Salisbury, England is near the halfway mark between London and Devon, England.
Istanbul
The halfway point between London in England (United Kingdom) and Annapolis in Maryland (US) is Bonavista. Bonavista is in Canada.
The halfway point between Troy, MI and London KY falls in or around Vandalia, Ohio.
India
Batley
Walsall
York.