Zonda - It's difficult to advise knowing little about your current fitness/abilities.
If I was doing 4 sessions per week it would include the following:
1) Long run (building up to at least 20 miles).
2) A marathon pace effort run, for example I might do 2 miles warm, 6 miles marathon pace, 2 miles cool down. I'd play about with the distances, but essentially I'd be increasing the distance of my marathon pace section, up to maybe 10-12 miles.
3) Interval session.......hard/max effort intervals. way beyond marathon pace. This week I've done half mile reps and shorter.
4) Steady state run. maybe an hour to hour and half.
This assumes can already run a bit. For some people just getting out and running regularly is all they need.
AM - never done Rivington half. I think I entered a marathon there last year but couldn't do it. It's a great place to train, hence why I do some ironman training up there.
John - yes.... I saw you had been set 20k. When you go longer get down to chorlton water park. There is a tap outside the toilet block for water, usually a bloke selling coffee and an ice cream van....winner. When you go even further, just get to one of bridges cross over and head back. Much better than running round in circles around alty.
Carterusm - I love the hills. I'm from North Manchester really. Brought up around Milnrow/Newhey area. Used to go running up into Saddleworth Moor, Blackstone Edge area. Unfortunately, hills now means me getting into my car to go and find some. I'm already time pushed with Ironman training, work, dad taxiing.....so it just doesn't happen. I occasionally drive out to Rivington, do some hill work on my bike and then run up to Rivington Pike. Done reps up and down Rivington Pike a few times.