Hello Stuart and welcome to the board and LCing.

Women can begin to set a goal weight by allowing 100 pounds for the first 5 feet of height and adding 5 pounds per inch over 5'.
So at 5'7", I could set a lower limit of 135 pounds. But if a person has a larger frame and lots of muscle development, that could go all the way up to 160. I am being realistic and set 170 pounds as my current goal. A goal weight can always change as you approach it.

You might want to set 'interim' goals or mini-goals and you can celebrate as you achieve each.

There are height-weight tables on the net (I have posted links in a thread here somewhere - use the Search function for the last few months.) They are of help IF they have a fairly wide range for each height.

Go to the Exercise Forum and see what BF targets those people are setting. Many people - Natrushka, for example - have really gone into the research on 'good' BF%

Good luck.