Welcome PM!
If your only wanting to lose 1.5st by Sept that's more than enough time. They average between 1-2lb a week, however, if you've never done it before you tend to lose more quickly although it does tend to slow down after a couple of weeks...
I've got 2 cookbooks but can't remember what there called - i'll have a search for them. If you sign up to the weight watchers board they tend to do recipe swaps etc on there.
Good luck!