Mounting your steed

Probably not...but by way of example, the boarding ladder on a Harrier is on the right side...but it's on the left on the T-45A/Hawk and the Toronado...and they are all (mostly) BaE built products...

I guess it really depends on the airplane, but I suppose in general, left mount is right.

Well on a Spitfire you have the hatch/door on the left, but on Typhoon's the door is on the right side. I belive the Hurricane also has the step on the right. A lot of Bubbletop WW II planes had walkways on both sides, so my guess is that it's your choise on those, otherwise that of a designer.

Some navy type aircraft mount from the right. That is the side closest to the island on an carrier.