The closest Junction to exactly half way is the A684 on the Route recomended By our Friends at Google Maps
I dont know if there are any services though, I have never gotten off the Motorway there.
By Road... Boroughbridge is considered the half way point between London and Edinburgh.
By Train it is about ten miles north of York on the track.
The halfway point between London in the United Kingdom and Edinburgh in Scotland (United Kingdom) is Liverpool.
Liverpool is in England (United Kingdom)..
Carlisle
Carlisle
Leeds in Yorkshire approx.
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.
Batley
The halfway point between London in England (United Kingdom) and Aylesbury in England (UK) is Watford. Watford is in England (UK).
Silver Springs, OH is the halfway point.
Frankfort, IN
The halfway point between Melbourne and London is Akyab, Myanmar.
The half way point is 39 miles in both directions. Where the A702 meets the A73 at a roundabout
Bolingbroke, Georgia
Edinburgh to Maidstone is 420 miles, so halfway would be somewhere around Leeds.
The geographic halfway point between London in England (United Kingdom) and Nottingham in England, (United Kingdom) is Northampton, also in England (UK). The halfway point co-ordinates are 52° 12' 8" N and 0° 55' 20" W.