Sorry, poor description.
It's faster in the scenario I mentioned because the road speed is higher.
The noise starts slow and speeds up as the car does. Most noticeable/loudest when speeding up at a moderate pace at just under 20mph. Past 20mph it kinda blends in to a whir/whine.
Letting off the accelerator between 20-30mph makes the noise a noticeable wuhwuhwuhwuh again.
Tyres are fine, swapped them around yesterday following my thread about the worn outer edge (swapping them has done nothing for the pulling to the left issue :( ). No bulges or uneven wear except for the very edge of one tyre.
It sounds mechanical, possibly central. Fairly sure it's forward of the seats, could possibly be under them but I don't think so.
I can't feel anything through steering that feels associated with the noise.
What do the following sound like when they fail?
I've had a failing wheel bearing before on a different car and that was a constant noise rather than a pulsing one. It also sounded grindy. Anyone had a pulsing wheel bearing noise?