Posted: 27/05/2014 at 15:21
I don't think you'll find a specific 11 month training plan, as the chances of anyone completing this would be close to zero. What you need to do is break it down into 2 to 3 month chunks and pick a specific goal for each period.
To work out what these goals will be will depend on you making an honest assessment of what factors contributed to your last marathon taking half-hour longer than your target time.
For example, did you start fast and then slow down or did you run a fairly even pace throughout (NB even the elite tend to run a positive split, so don't be too critical if you ran the second half five mins slower than the first half). If you ran fast then slow, this means you need to improve your endurance and would benefit from longer, steady runs. If you ran fairly evenly you need to build speed, so you need to have an interim target of a sub 1:30 half marathon to achieve your 3:15 time.
I have to recommend the Pfitzinger & Douglas "Advanced Marathoning book" as it covers all the things that contribute to improving your marathon time, including stuff like diet, core strength and race day planning.
You also have to be willing to commit to the work involved, most sub 3:15 marathon runners will be clocking more than 50 miles per week during their training. This takes significant time & energy, and is difficult to accomplish if you have an already busy lifestyle.