I posted a while back about a noise I've got, I've still not managed to pinpoint the problem, and I'm begging to run out of both ideas and patience.

The car is a 2000 1.7 Puma, if that has any significance on the problem (don't think it does really)

Symptoms:
Getting a regular knocking coming from the front of the car, and more to the n/s than the o/s.
It's always relative to the wheel speed. (i.e. sounds like there's something stuck in the tyre thread)
Most noticeable between 20-30 mph, it seems to go over 30 mph unless I really listen for it, then is extremely faint, and sounds more like the drone you get from a dodgy wheel bearing.
Can feel the noise as much as hear it through the car.
Louder on bends to the right and roundabouts, and sometimes goes completely on sharper bends to the left.
Louder on coasting and braking than it is on accelerating.

Causes ruled out: (i.e. noise present both before and after)
N/S wheel: changed for a different wheel.
No loose wheel nuts.
Brakes and pads all fine, no sticking or warping.
Brake calipers are not loose.
N/S wheel bearing - changed about a month ago.
N/S driveshaft changed as was knackered, but didn't solve the problem.
Diff & gearbox (& clutch) changed last week. So unless I've been really unlucky and picked up a gearbox with an equally knackered diff, it's not that.

My mechanic is scratching his head at the moment as much as I am. I know it could be the bearing or driveshaft on the O/S, but there are no obvious issues with those on inspection.

One of the front suspension mounts has a small amount of play (can't remember which one offhand - might be the N/S) compared to the other.

Any suggestions would be appreciated before I end up spending more money, or get that pissed off I end up taking a sledgehammer to her.