For a stand alone FRTOL it is 12 months. If you combine it with the PPL and make the application concurrent then you have the full 18 months to complete "ALL" exams and then have 24 months from the last exam to complete the application.
Its all in the AIC 19/2004:
http://www.nats-uk.ead-it.com/aip/cu...4_W_019_en.pdf
Its not a Oral, its an RT Practical there is a difference!