Rosie, you are quite a conundrum. The times you are running would indicate to me that you are more than capable of running considerably FASTER than sub 3.30, and yet despite having done a lot of marathons, you haven't achieved this. I can only guess that this is because you are in a constant state of low level fatigue and are therefore not performing to your potential when it comes to your key races (not helped by living on sports drinks, methinks... Ruth - help her! )
I can see you are finding it hard to take rest days but as everyone on here has stressed, rest is when the body gets fitter. Training is basically about breaking the body down. You give the body a stress that puts it outside its comfort zone. It then as to go 'oh blimey, better make some changes so I can cope with this next time round.' BUT. a) the stress has to be just right - not too much and not too often (or too little, and not often enough but don't think that's an issue for you!) and b) you have to BUILD IN rest, as this is when those changes or 'adaptations' take place.
OK that's the telling off finished!
So looking ahead to week 3. This is slightly provisional, as I've said that we'll review Rosie's paces, based on her 5km race result on Sunday.
Week Three w/c 9/1/12 (35M)
Mon Rest (+ strength training)
Tue 7M CONSISTING OF 1M jog, then 4 x 1M (or 7 mins) fast, with 400m (3-min) jog recoveries, then 1M jog
Wed 7M slow
Thu 4M steady
Fri Rest (+ strength training) COMPULSORY NO RUN DAY!
Sat 4M easy
Sun 13M easy (I recommend trying out sports drink or gels on these longer long runs)
The only difference in Rosie's prog compared to the sub 3.30 schedule is that the 13 mile run is an 'easy' rather than a LSR. And I don't think anyone else needs to be told to have a 'compulsory no running day' 