Hi JamieH .. will enjoy feedback from the 8k event 
re: long runs .. I am a strong believer in the individual runner's efficiency while running ... when you run at the lower heart beat, it is important to note what your body is doing .. often, slower running leads to poor efficiency and actually puts the body under stress .. what you can do is consider breaking your runs down into 20 minute segments, taking a break between the 20 minute segments .. stopping to take a stretch, water and allowing the pulse to drop then starting up again, this way you will have a lower pulse with more efficient running .. then once you start building on the fitness increase the segments to stopping every 30 minutes
hope this helps
TheEd
re: long runs .. I am a strong believer in the individual runner's efficiency while running ... when you run at the lower heart beat, it is important to note what your body is doing .. often, slower running leads to poor efficiency and actually puts the body under stress .. what you can do is consider breaking your runs down into 20 minute segments, taking a break between the 20 minute segments .. stopping to take a stretch, water and allowing the pulse to drop then starting up again, this way you will have a lower pulse with more efficient running .. then once you start building on the fitness increase the segments to stopping every 30 minutes
hope this helps
TheEd