Thanks for the comments folks...
One of the first things I did was to throw all her food out and replace it, along with giving her cage a super clean and I also bought a very good air purifier.
Jules you're right (from what I have read), asper is usually caught when the bird's immune system is low. But I also read that they can get it if exposed to large quantities of the 'spores', and thinking back, I think I may have given her some strawberries that were beyond their best. I fed her strawberries one day and when I went to the fridge the next day, they were mouldy! So I guess they would have been bad the day I gave them to her, especially in her cage and not in the fridge. (I wouldn't mind but I'd only bought them 2 days earlier from Morrisons!)
As for her treatment, the vet said that there are 2 different anti-fungal medicines available, the general one and a more recently available (4 years or so) one which is supposed to be much better - but it also costs 5 times the amount of the general one, Ouch!!! Anyway, I went for the expensive one.
I wasn't expecting to see any rapid results but the day I picked her up from the vets, she seemed a hell of a lot better (maybe the preivous bout of anti-biotics were kicking in) - strange! Anyway, she's been on the anti-fungal meds for about 5 days now and she seems to be getting slightly better, she's trying to talk alot more (although her voice sounds horrible, painfull) and she has lots more energy than before. She's flying more and playing with her toys more etc. Generally she seems 'happier'.
So, she seems to be going in the right direction but we've got a long road ahead of us!