Thanks all. We have the letter. £15 for four lines saying she has a very nasty cough which is making her unable to sleep. I hope it's enough!
The inhaler is helping when she has a bad coughing fit. She has lung inflammation and it's meant to reduce it too I think. The codeine phosphate which was meant to make her drowsy and suppress the cough did absolutely nothing sadly so she had another bad night 
Saying that, I'm really proud of her and the way she's dealing with all of this on top of her A Levels. She had her extra subject AS today and it looks like she wrote up a storm today as she needed two extra booklets!
Night off from revision tonight for both her and Gcse sitting DS. She's gone to her boyfriend's and I hope she can break the coughing and insomnia cycle soon.
Thanks all for your kind comments, I feel like you guys are practically family in a way, we're all looking out for each other and that's a lovely feeling