To be fair, there is a conclusion, but it states:
There was insufficient evidence to establish why the aircraft had behaved as it did and why the accident occurred.
As the aircraft in question is a home-built/ULM design, I believe that the AAIB is not obligated to fully investigate such accidents, seeing as there is less of a regulatory structure to deal with possible airworthiness issues (don't quote me on that though). With that in mind, the report is still quite comprehensive. Looking at the images, it's a good thing the pilot managed to survive the accident.