can't remove flymo turbo compact 350 impeller. any ideas?

Hi guys! I have a flymo turbo compact 350 and the belt has snapped. I bought a replacement belt, and after watching an instructional video was confident I could fix it. However, after removing the bolt for the blade, I found that the impeller would not come off! I've tried searching for hidden screws, brute force, and wd40 but to no avail! Is anyone familiar with this problem and know how to fix it?
Many thanks!