Try getting someone to hoover in distant rooms, while you stay with the dog and continually give her treats.  Slowly, watching her reaction, bring the hoover slightly closer and continue to feed treats while the hoover is on. 

I will try that onetwothree, thanks.....................although she tends to not eat treats when she is very scared........on a few occasions she has done this!............should I cuddle her to reassure her...or not??

Shaz
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No, don't cuddle her to reassure her - what you'll be doing (in her mind) is agreeing with her that there's something to be scared about - that her fearful behaviour is correct and justified, which is quite the opposite of the message you mean to put across.