My first 10K was six years ago just to give it a go, and provide some focus for my occasional visits to the gym. Lessons learnt (1) Get a digital watch - I checked my time after the first K and realised I didn't know to the nearest minute how fast I was going (2) Pacing - spent the last 7K of the race with waves of people passing me. Still, I was hooked, and have been improving in fits and starts ever since.
Abbers, your posts have prompted me to drop back in after a few months out of this thread. My last 3 half marathons have been 92:11 (Ealing 2012), 90:17 (Reading 2013, PB), 91:16 (Ealing 2013). And I have signed up for Brighton 2014 which will be my first full marathon. So looks like I'm in a similar situation. Good luck on Sunday!
I went for sub 90 on sunday, but I knew it was a long shot given slightly too light training in the summer (more like 30 mpw than 40), including 2 full weeks off in August. I hung on to target pace until about mile 8 and then began to lose touch. Finished with my first ever half marathon positive split.