Hang on hang on hang on; Gaz, what's all this about marathons at New Year?!
Scott, get some 1km-1 mile intervals in at 5k-10k pace, that would do the trick (if you are not already). I actually think that I couldn't get my 5 or 10k times down any easier by doing specific training, I'm a definite advocate of endurance training and a tempo a week with an interval session when you can, will stand me in good stead. Unless I wanted to run for Team GB, I'd rather do what I enjoy and just hope it helps with shorter races.
Mattl - really??!! Blooming heck. How's the foot by the way? You made a definite decision re marathon?