Well, I'm glad to hear you've not given up on this, but the advice is still the same as last time - Walking up hills is the best training.
I don't know how much your fitness has improved since your Hope valley walk, but while running up hills will certainly improve your cardio fitness; it uses different muscle groups to hiking. (Really..)
You'll still need to get your 'fuelling' right (IIRC that was maybe the root of your difficulty at Hope??) But on the whole; keep at it and keep walking. Have you tried cycling? Again, good for cardio, but again.. more different muscle groups. You wouldn't think you'd that many different muscle groups in your legs..
Keep it up