Im not convinced doing the 5k every single week will aid your chances, but if you do that, maybe have that as your 1 fast session of the week, and do the rest relaxed.
Then when you find that you're doing a nice 25-30miles a week, with no issues, you can add a more detailed speed session in.
The vast vast majortiy of runners never get under 16mins for 5k, so i certainly wouldn't count on getting under that time within a year.
I'd be thinking more sub 18:30 as a 2month target, and then 18:15 as a 6month target etc....
And join that athletics club asap....i'm sure they'd have you swap the 5k park run for a hard track session most weeks..
Edited: 11/08/2012 at 15:21