The first thing to note is that the CAA is implementing the rules ahead of some EU countries, the 2015 timeline is to ensure all countries have completed the implementation. An example is the issue of new EASA pilot licences has started in September.
The next step is to contact your AME or the CAA and ask them to confirm the start date, followed by advice on how to proceed.
Finally you need to note the protocol the CAA have published, specifically the how to comply with the rules they have set out, acceptable treatments and required medical reports. Not all medical conditions or severity will be acceptable or suitable for flying, remember mental health will be assessed on a case by case basis.
Note to mjd1, as you believe the condition is classed as reactive then try the CBT route first. This group of depression illnesses is quite responsive and will help. Unfortunately it is perhaps not as effective on endogenous forms of the illness, which are more related to mood hormone imbalance