There isn't even a standard to force you crazy British to call it a wrench 🙂
Open end wrench/box end wrench
There are some head "clearance" standards (based on a composite study of commonly available ones) I guess in the machinery handbook from the SAE aeronautical drafting manual... nothing for metric in there but this guy has done some work... http://www.roymech.co.uk/Useful_Tables/Screws/Head_Clearances.html
This is my definition of a "spanner wrench".
Maybe cbliss.com has what you need.
http://cbliss.com/inventor/Parts/Tools/index.htm
I am looking for spanners or combination spanners, (wrenches are for plumbing ... see picture below. They do come in standard lengths, theoretically you tighten each fixing with the same force, (human power) and the larger the spanner, the longer the lever hence the correct torque for the size of bolt you are fixing, (this is my understanding anyway, hand tight, then ****)
I could always go to the workshop and measure. We use impact sockets for our socket sizes as they are the largest we would put on a fixing