Hi sarahrunner, congratulations for entering yourself and your other half into Brighton for next year, and all the best for your training over the next year - it is one year to the day that we'll be toeing the line - in fact, one year from now I'll be in the car half way to Brighton!
A year to train for a marathon is definitely doable - it'll give you plenty of time to build up the mileage very slowly so your body can adapt. As a rule I normally start to get serious about my marathon training about 4 months before the event, but I've been running since '92 and my body kind of knows what to expect!
My advice would be to spend the next 7-8 months enjoying your running, gradually increasing the mileage whilst including the odd week of reduced mileage to give the body a rest, before following one of the training plans you can find either on Runner's World or in the 1000's of books there are out there on marathon running. I'd also advise including some races in your running so you and your other half can get used to running with a lot of other people around you - start with Parkruns and move up to a decent sized half marathon sometime later in the year.
Also, if you're not a member of a club you and your other half could join one - you'll find there's plenty of 'been there, done that' veterans of marathons that'll give you advice along the way!
Hope all goes well over the next 365 days of training!
Ah-ha! Good spot Toby3, thanks for that - just checked my split times, and found they stopped after 25k - unbelievably I didn't think to check the back of my number until now, and guess what - no chip!
Not that bothered really as I had my watch going from the time I crossed the line so I know my time, and I roughly know the time by their clock - they should be about the same but I stopped my watch for a couple of loo breaks! (Bit of cheating I know, but I always think that technically I wasn't running at that point! )
It's perfectly natural to be nervous about running double the distance, but I'd say that if you're running a half in just over 1:20 then your a more than decent standard! To get to where you are over 13.1 I assume you've been able to sensibly schedule your running, so with the right advice stepping your training up to marathon racing shouldn't be a problem.
One piece of advice would be to join a club if you're not already a member of one, and see if there is anyone who is around your ability level for the half who has experience of moving up to a marathon, and pick their brains and possibly train with them. Most clubs also have qualified coaches who'll be able to give you advice as your training progresses, which would be much more valuable than reading an online training schedule or snippets of advice.
Above all, enjoy it - marathons are a great experience, and I reckon you'll do a great time at Edinburgh next year - all the very best with you training over the next six months.