AJB,
I was the same way, what is normal ???
Just had a mechanic friend look @ mine, he put a jack under the engine on the N/S (Passenger) and was able to move the engine. Not by much, but we did find that fluid from inside the mount on that side started to come out.If you look at the engine you'll notice it lifts on the passenger side, so the mount on that side is constantly getting abuse.
I would of thought if the Front prop was on the way out you would feel it under the drivers side & it would vary with speed.Could be wrong though.
Have U checked the N/S drive shaft for play ???
Chris.