Pete - same here. Exact. Non-productive cough. Going on and on and on. Went on
for two years. Had doctors implying 'it was stress related'...!! Hoarse voice - rasping, sometimes disappearing to a mere whisper. Dry mouth - sometimes tongue tongue stuck to roof of mouth. Dry eyes - have the punctly plugs, bliss, no more streaming eyes and all those eye probs where sometimes I couldn't hardly 'see' the PC screen! Finally
FOUR consultants later (heck you couldn't invent this stuff) I was eventually referred to this whizz guy, who checked out my vocal cords on the EMG machine (electro myelogram - checks out vocal cords via a hook up from sensor pads placed around the throat; then these in turn are attached to electrical equipment and hooked up to a screen). Interesting equipment and very interesting consultant runninng the tests - think this was his own breakthrough in using EMG machines in DX laryngial problems (he is ENT and does a lot with opera singers and theatre persons). Lo and behold, Sporadic Dysphonia AND tied up with Sjogrens (was V. glad to cock a snook at the disbelieving clonker doctors

)
Now for the weird part. My neck has been throwing wobbies, nuisance. Painful, and getting mild but persistent headaches. So, was referred for some physio. The phyotherapist *refused massage or ANY kind of 'hands on' as there is a slippage of C2 over C3 - she was real nervous that she might cause further slippage and then I'd be in a right bowl of soup with possible paralysis! OK. So, put me on the tens machine. Started with the continuous buzzy-fuzzy-tingly setting, then, went to the pulse. After the first pulse session, I suddenly noticed that my voice was clearing up. Then had another session and a third session.
My voice is 'practically' back to normal, and have hardly coughed AT ALL for a few weeks now. Huzzah!
Seems to have cracked it. Going to get my own tens machine, but will have to wait for me to save up for it.
But yes, know exactly 'where' you are coming from. BTW - sucking mint sweets helps and also, having a large bowl of water in the bedroom, keep it near to the radiator: humidity. Plain warm water to drink is quite good as well. Keep the vocal cords lubricated. DON'T drink Coke or sodas, pleeeeeeese. Plain water, and preferably warm water. OK?
Molly
Keeping on Keeping on