In my experience finding the right training plan for yourself is trial and error. I've never ran to a HR/Time based plan, but there are plenty of training plans that advocate exactly that. I go over three hours on some of my longer long slow runs, but there are plenty of articles about that suggest doing training runs longer than three hours actually have a negative impact. Personally I ignore those reports as I've ran all my best times based off five runs of 20 miles or more in training, all of which took me longer than 3 hours.
I've seen and heard of people completing marathons on all sorts of plans. I'm sure you'll be fine. The first one should always be about completion. It's a great feeling to cross that finish line for the first time.
Alastair - I hope your injury issues are behind you now. I had an injury plagued time of and my training paces dropped off the edge but have battled back since around March this year running my second fastest marathon in Paris in April and setting a new 10km PB in May. It's great once you can get past those injury problems.
Nurse - Well done on your swim.
I enjoyed the drop in temperature tonight. Overcast and slight drizzle made for a much more enjoyable 9 miles tonight.
Will - The website pretty much crashes each year when registration opens. That said it's not a race that sells out in hours. In fact this year you could still enter in February. The only drawback to not sitting on the web the second entries open is the cost. Unlike most races it's not a fixed price entry. The first 10,000 places go at a cheaper price and then the price increases, so entering later can cost you an extra 10/20 euros.
The best thing to do is to create an account at the ASO website before entries open ASO that is where you enter the race.
I'll keep an eye on the Trossachs Ton, that sounds very tempting. I'm sure you'll love the London Ride100.
I've ridden the Etape Caledonia before in 2011 and it was the event I've enjoyed the most. I wasn't bothered about time and just went out and enjoyed the scenery and enjoyed cycling along chatting to folk. It also didn't leave me physically shattered like a marathon does and I can eat what the hell I like on the bike and not have to scoff energy gels to keep going!