Rendering image sequence to disk is stupid slow!

I’m trying to render 360 panoramic video in UE4 using the built in panoramic plugin. While trying to set this up, I accidentally rendered to 1080p non-panoramic format. It took something like 20-30 secs to spit 300 frames out.

I then managed to get it outputting 360-format (still very lowres) but the render time had shot up to 30 secs a frame which is about double the time it would take in blender and kind of defies the whole purpose of switching to a real time engine to speed up my render pipeline.

I switched back to non-panoramic mode and hit play again and now even the non-pano shots are taking about 30 secs a frame. Any ideas for what I should be looking at to fix this would be much appreciated