According to a BMI calc I just did (I am also 5' 7") BMI of 25.1 is achievable at 160 lbs (11 stone 6 lbs) although I am also personally aiming for around 12 stone (ish).
And according to this BMI calculator at a weight of 12 stone 12 lbs (180 lbs) and height of 5' 7" BMI comes out at just above 28, not 30:
Calculate Your BMI - Standard BMI Calculator
You might be lighter than you think already , Happy Days !!!