Funny about the Lynx - that's where I found out there was no NATO standard stretcher.
Seems like the Army / Navy requirement for the Lynx called for it to be able to carry a NATO standard stretcher. The Lynx dimensions were also being very heavily defined by the military, resulting in a problem. How to get the stretcher into the cabin. Someone clever in Westlands discovered there was no NATO definition - everyone was using the US military stretcher size by default without it being written down, it seems. So they were able to get out of the requirement - a US stretcher will fit diagonally, it seems. The UK then somehow adopted the Neil Robertson (name may be wrong) stretcher, which was basically strengthened cardboard with no bracing to make a flat surface. when you picked someone up, the thing basically curled around the body.
Worked OK unless you had a shoulder or back injury, as happened to the first F-18 accident pilots who happened to land next to Middle Wallop and get picked up in those stretchers...
(sorry - I know this is off-thread, but it shows the issues of interoperability)