Adding buttons to steering wheels can be a right PITA: I had a similar problem when trying to use steering-wheel mounted buttons to operate a programmable water-injection controller...!

You can't go the F1 route (socket in the centre of the steering shaft, inside the splines): you may have to settle for the coiled-cable option., like the rally / BTCC cars use?
Not quite OEM, but by far the simplest solution!

re: the opticals......is your car fitted with an electrical PS pump, like the Mk3? If so, it could be to do with the control of that..?