Ed - Everyone is different in running as in most things. To do a marathon 7 months after starting running would be a great achievement. A first marathon is special, I think. Not many people would suggest setting a demanding time target, but even so one does need to run a lot just to get round on the day. I think that a full marathon is about 3-4 times harder than a half.
From memory I trained 30-40 miles per week for my first marathon and was quite happy with the result. For my most recent marathon I followed Pfitzinger & Douglas up to 55 miles per week and was even happier with the result.
I'd suggest you see how you feel after your half, and target a local 20 mile race in a few weeks. I don't know if there are any; oddly enough(!) there don't seem to be too many 20 mile races round here over the summer. A twenty mile race would give you an idea of how you're getting on.
Even if you can't find a 20 mile race I suggest doing a few 20+ mile runs before the day. Most people find the time to train if they want it enough.
Torquayrunner - Good luck. I dislike Lactate Threshold runs more than any other sort, worse by far than intervals. When I do them, which is rare, I usually do a 2-mile warm-up and 3-5 mile cool-down at recovery heart-rate. I find training to heart-rate very helpful, especially when keeping to recovery, i.e. low, heart-rate. It takes quite some time for my heart rate to get down to recvoery levels after a Lactate Threshold run, but I do think a long recovery afterwards helps.
My race speed for 10 miles is far closer to my half-marathon speed than my 10K speed. I don't know if that's what the sites show. However do bear in mind that everyone is different. I think the worst thing you could do is go too fast in an early Lactate Threshold run and injure yourself. Thus I'd suggest being cautious about target speed.
Lisa123/ Torquayrunner - Thanks for the info about accommodation.
On training, I used Pfitzinger & Douglas (P&D) up to 55 miles for the first time at Brighton 2013. I really liked it and intend to use it again. Ideally I'd step to the next level which is up to 70 miles per week. I probably won't as in the past I've been injury-prone and indeed have a couple of minor injuries at the moment.
I think the P & D book is worth buying anyway, even though I'm at the slower end of their target readership. From memory the reviews on Amazon are very good so I'm not the only one who thinks so. It is for faster runners, or at least for those who are confident of finishing, and looking to improve their time.
The schedules are based on distance, not time or speed. They are also based on heart rate bands, which I took some time to get used to, but I now think is a very good idea, because it helps prevent going too fast to much of the time.