HM training

Hog-mouse

Three Forts Half Marathon 1st May 2011
According to the map I've drawn using Anquet there is 1800 feet climb on this race.

I wish to complete sub 2hrs.

My last long run was 11.5 miles with approx 1800 feet climb in 2 hrs. My current average weekly mileage is approx 35 miles. (last week 40 miles) I intend to build up to a weekly mileage of 45 miles with a long run 15 miles with 2500 feet climb. (next race is going to be tougher)

Question. What is the best way forward with traning?
Should I work on speed on the flat - eg track intervals / tempo run?
or just do off road hilly runs - shorter distance with a bit of speed?
or hill reps? 

I do some hill interval training with my club which is situated in a fairly hilly town so every club run involves some hills, also get to up the pace a bit at times. Sunday runs are short, off road runs at very easy pace - usually undulating. (running over South Downs). I can use track on Thurs but 15 mile cycle ride usually tires me out so I don't tend to perform well on track.

My week is usually my own and my training is quite flexible. I work casual hrs but comute by pushie asI don't drive