Glow worm 18hxi boiler with f5 fault light?

After a problem with my fuse box, my heating is not working, I have checked the boiler (Glow worm 18hxi) and I have a flashing f5 fault light.
I have reset it several times as your site suggested and it seems to be working but there is still no heat to the rads but do have hot water.
Please can you help...
Regards