Hi Mark welcome to the site. You have a bit of time to build up for your first HM, I just completed my first a couple of weeks ago. To achieve your time band you need to run the full distance at around 7.30 mins, I completed mine in 1:39 in the blistering sunday heat.

You need to start building up your mileage, I run six days per week using alternative easy/hard days with one run per week being a long run either at an easy or steady pace with the last 4 weeks before the race running the full distance or over. This was included in my weekly overall training mileage of 40+ miles.

I also found that the day before the race I carried out a hydration programme that meant drinking quite a bit of water, this paid dividends on the day as I did not need to drink a lot of water before the race, so the toilet visits were not required and this carried me through the race.