Ruth,
I often have days like that, thirsty as hell etc.....sometimes feels like you've got a layer of 'ming' on your tongue/roof of your mouth?
I find a really strong mouthwash used before and after brushing REALLY helps....but the mouth/breath sprays make it worse!
Cream makes my mouth feel like it has a filmy layer on it too...kinda greasy.....as does tea with sweeteners in it....
I get quite dry lips too.....but thats pretty easily sorted!
SO, aye, You're not the only one who gets cotton mouth!