I'm following the official training plan, and it seems a good mix. I did 70 minutes running in the rain last night. Did about 6.5 - 7 miles (hard to tell exactly). It started slow and a bit achy, but finished fast and lovely. I have been trying to do the fartlek stuff, but picking up my pace makes my asthma kick in quite fast. There is exactly 1 month to go before the big day!!