How are you sleeping? I always find that this kind of thing stops me sleeping, which makes the whole next day an endurance test!
My fallback options include
Vitamin C (I go for the naturally derived ones in relatively small doses, rather than the synthetically produced mega doses)
Zinc
Echinacea herb tea. Some of them actually taste OK!
Lots of hot drinks
Chicken Soup (the universal panacea)
and when I just need DRUGS!!! I go for the capsule version of Night Nurse. They knock me out for a good 8 hours of restful sleep. I don't touch the Day Nurse stuff because they shove caffeine in it, and I don't touch any of the other Night Nurse products because they either have sugar or sweeteners or other rubbish, but those Night Capsules are magical.
But check with your pharmacist when you buy to see if they are OK for Ds. They were the last time I bought some, but you never know if they have sneakily changed the recipe, do you?
Re the Lemon and Honey, I would be tempted to say Go For It.
I mean, how many grams of carbs does a teaspoonful of honey have? 5g? (thats a guess). Can't see 5 g doing much harm, especially when sipped slowly... just don't go overboard.
Hope that helps.