Lost headlights, hi-beam, wipers and washer fluid pump

Hi all, really struggling with diagnosing this one. Car is a 1993 1.8lt Cabriolet.

When I bought the car 10+ years ago the intermittent and low-speed wiper settings did not work. This didn't really bother me as I didn't drive in the rain and when I did just used high-speed.

However, over the last month I have lost all wiper speeds, the windscreen washer pump, as well as the headlights and hi-beams.

The parking lights and indicators still work.

The high-beams also work if I hold the stalk in position - ie high-beam switch no longer toggles them on and off.

Other electronics in the car appear to work fine.

EDIT: just did some googling - interior fan is not working either. I imagine all of the above are routed through 1 relay? Does anyone know which one?

Here's what I've done to try and fix so far:

 - Checked all fuses - all seem to be ok
 - Checked both headlight bulbs - ok
 - Disassembled columns stalks and cleaned wiper switch contacts - they were a bit dirty, but cleaning them made no difference
 - Cleaned earth contacts (the ones I could find) in the following locations: top of rocker cover, on frame underneath battery, top of scuttle panel

I've also recently:

 - Replaced fusebox (1+ year ago)
 - Replaced washer pump (3 + months ago)
 - Replaced headlight rocker switch (3 + months ago)

We've had a lot of rain recently and the car has had to be outside during some if it so I am suspecting some corrosion is the cause.

Would anyone be able to point me in the right direction with this issue?

Many thanks in advance.

Ignition switch, and or the load reduction relay are all responsible for the above things.

I would also suspect the rain drains being plugged, and or the antenna as possible areas of where the water is migrating into.  The antenna if it has been replaced would need a drip stop loop, you can check it by removing the inner fender cover and see if that is one of the areas.  

see: https://www.vwvortex.com/threads/the-x-circuit-from-the-ignition-switch.6761577/

Drip stop loop.
https://www.volkswagenownersclub.com/threads/why-is-it-raining-on-my-feet-i-just-changed-the-antenna.108841/

Ah yep, that's most likely it. Thanks Briano!