ADARE TO SURVIVE isn't going to be a like a walk in the park and proper training will definitely help! We have outlined a few pointers below.
Our Fitness Partner DN Fitness is available to provide training tips and hopefully some boot camps to ensure you are giving yourself at least fighting chance!
Legs, legs, legs! They are going to have to carry you for the 7.5 K so you should do some running sessions once a week, building yourself up to 8K on roads. You want to be comfortable running this distance and then try doing it cross country, up hills etc. The more varied you can get it the better.
To increase strength in the legs you wont go too far wrong by incorporating squats and lunges into your weekly workouts - starting off with bodyweight with progression to weighted variations.
Upper body strength is the next area you should look at trying to improve with a combination of weights sessions and bodyweight exercises like push ups - don't worry too much though - due to the nature of the event everyone helps each other out so there will be lots of people, as well as marshals, available to hoist you over the different obstacles if you are struggling!
Why not check out Lizzie's Total Body Workout to help you get in shape.