Louise
I have attached the guide in the the that Leah's Mom refers to, you see that you need to take it slowly, it may also take longer than the suggested 2 weeks.
Your Lo should be on a 4hr EASY by the time he needs weaned anyway - I believe the absolute min. in the UK is 17weeks, unless of course your doctor has specifically said to start any earlier.
I think that is the best way, watch his cues for a couple of days and see how often during the day he needs fed, I also did this.