You guys worrying about time running out for setting absolute marathon pbs - fear not. On runbritain rankings you will find loads of mv50s setting sub3 marathon pbs, quite a few mv55s and even the odd 1 or 2 mv60s and mv 65s!
I've always assumed that it is easier to hit high WAVA percentages with the longer distances than the short or maybe that is an age thing? My WAVA for the marathon is 83% but for shorter distances it isn't even worth working out.
If you want motivation for losing weight, it is generally said that every pound you lose is worth 2 secs/mile over the marathon distance. The bad news is that for every year you are over 50 you lose 4 secs/year.
As I only did my first marathon at 50 I have had to lose 2lbs/year just to stay still.
When I started running I was a hefty 12st10lbs (5'7" tall). When I set my current pb I was 9st7lbs