Yes,
I'm not conversant with any Ravenheats, fortunately nobody seems to have fitted them in Scarborough despite the fact they are up the road.
When you say you followed the fault chart did you comprehend the importance of each step and check it acurately?
If the boiler has a low pressure sensor, and also an overheat sensor, then as posted above these two items are a very important step for you. The fact that the fan isn't coming on, for most boilers implies a different problem to a stuck pump, because the sequence pcb's go through on most boilers before allowing ignition is ; check aps functions properly, then check fan functions properly using proved aps, then check pump runs properly via flow sensing, then commence ignition sequency.
The low level sensor and OH stat interrupt right at the start so non of these checks are made.
You check for continuity across certain pins with an ohm meter with boiler off, or you check for voltage, both sides of device, boiler on. Trace where you fisrt lose your voltage, you might even find your self back at the fuse.