Bit of a strange one. I get a bit of steering wheel wobble very similar to when wheels are out of balance, but it's not speed related in the same way. If I brake hard, it disappears and doesn't come back on the same day, but will reappear the next day or so.
Will whip the wheels off for a look, thinking maybe sticky calipers? Any thoughts or anyone had similar?

yep,possible sticking pads,we get this on roadside breakdown jobs.

Just had a chance to check out the brakes. The front left caliper is seized solid, can't get it to budge even with a large G-cramp. Under the seal is full of rust. Hopefully that will be the cause of the strange wobble. The right hand side is just movable with the cramp, but will order both left and right Pagid calipers and go from there.

Replaced the calipers and both flexi hoses and all is well again and no wobble.

That must have been really heavy corrosion.