Gavin it's because of the wooden structure that worries the CAA. I went through the same problem with the L-18 even though an aero engineer checked the whole design!
The metal and tupperware aeries can be mathimaticaly proven (even if all the fastners are not installed correctly, or rivets not drivven to spec making the thing weak) wood is just not that eazy , and I was told by a CAA official that the glue joints could be a problem, hence the test
You need to only test 1 wing and attach points for them.take alot of photos from every angle at 25%,50%,75% and full load and check full movement on aileron.
Even though the Part 24 clearly states that a load test is required only for a prototype or first of production plane (wich yours and the L-18 isn't) CAA still want's it and you will not get away without it!
Good luck
Theuns
Ps. I have pix of my load test ,i will e-mail them to you if you want.