Completed week 4 the other day, actually found by the third day I could do 5 minutes fairly easily and the interval walk wasn't needed. I'm actually starting to recover my breath faster. Starting week 5 today.... the jump to 8 minutes looks fairly scary but I'm sure now that it's just a mental thing, but am trying not to think about the week 5 run 3 20 minutes run...
Have also found I run much better in the evening than the morning - I can go further and seem to have more energy. Good running everyone!