Ok, heres a question that you guys may be able to help with:

Do a ships Warp Engines provide propulsion in the warp as well as transit between realspace and the imaterium or does a ship need it's plasma drives for propulsion once in the warp?

If I read correctly according to the rule book yes... but I think its not to cover distance, as the advantage of the warp is that space and time collapse and area mutable variable and... well chaotic. They are more used for navigation and pointing the starship in the correct direction

I think I read in the Rt book that once the ship entered the warp, the main engines were offline. I will find the exact reference.

Grand Inquisitor Fulminarex said:

I don't have the page number but that's essentially correct. The Plasma Drives don't go offline per se, as they're needed to power everything onboard, but they're not used for propulsion.

I read that last night.

Likewise, there's always all kinds of mentioning of warp tides, warp currents, ships finding favorable currents and arriving in a speedy manner or ships being "becalmed" and unable to move much. This seems to suggest that while in the warp, movement is more a matter of translating and navigating the ship to warp currents that will actually move it. Very age of sail and all that.

I guess the warp engine translates the ship to the currents that will carry it along until the warp engines translate the ship again though it's probably more complex then that.

Excellent, thanks for clearing it up for me everyone, much appreciated