Thought it might be an idea to flag this here, though you may have already come across this:

I'm suffering from an irritating cough at the moment, and decided it was time to get something to soothe it. I had a look at all the cough syrups etc available at my local pharmacist, but they all contained sugar

So, I asked if there was by any chance such a thing as a sugar-free cough syrup - and yes, there is It's called PAVACOL-D and is normally given to diabetics. It's not usually on show on the shelves, but it is something you can ask for

It contains saccharin (which some people try to avoid) and sorbitol - and it does taste revolting but it's certainly helped with my cough