Hi Graham
This
http://www-writing.berkeley.edu/tesl-ej/ej30/r2.html is a summary by Elizabeth Cramer of Brigham Young University, of a series of textbooks on writing which I have used many times with great success with students in Thailand. They are suitable for students from Grade 10 through university 1st & 2nd year English Foundation courses as part of a bachelor degree programme.
There are three books in the series but according to the level of the sudents, you can start with any book. Dependiing how you pace the lessons, each book should offer enough material for your 30 - 40 hours. For your ladies I would suggest the middle book:
Ready to Write: A First Composition Text (3rd edition)
K. Blanchard & C. Root (2003)
New York: Longman
Pp. iv + 156
ISBN: 0130424633 (paper)
Dist.: DK Book, Bangkok
And here is the publisher's catalogue page for the series:
http://eltcatalogue.pearsoned-ema.com/Course.asp?Callingpage=Catalogue&CourseID=QZBuild a house in Thailand on a teacher's salary?