To me, everything that has been said makes sense. However, steering wheel vibration (when not braking) is usually wheel (im)balance associated, and I’d still be trying to eliminate that possibility as a first port of call.
You say having the wheels balanced has not got rid of the problem, but has it reduced or altered it at all? At what speeds is this vibration worse? Can you ‘drive through it’? Does braking influence it? As has been asked, are the tyres a marching pair on the front? Has it always been the same in your ownership, or has it suddenly developed?
Wheel alignment? This would be low down on my priorities, but a thorough wear check of all the suspension and steering components would be nearing the top, if a double check on balancing etc. doesn’t cure it. In my book, wheel alignment should only be carried out after an inspection to prove all associated components are serviceable. Yes, I know it should always be done, but usually the first job is to simply hang the wheel ‘gauges‘ on the wheels!
Hope some of this helps.
Kind regards,
Austin.