While waiting for 4 min for last post above to load I was sat here looking at your loft -
Shouldn't there be horizontal and cross bracing on those trusses - Mine looked like yours and surveyor picked it out when we bought this house - I have cross braced every 4th truss -ie - bottom of first to top of 4th -- There is no triangulation to trusses to stop them leaning one way or the other in a very strong wind.
Dave
The floor joists complete the triangle