Kevin, 100% realistic. If you offered to pay me £50 to get you sub 2hours I'd go and spend the money now it's such a given 
Choice is yours really on approach.
1) run all runs as fast as you like, vague ideas on speedwork and tempo paces. Will get you short term gains, whilst knackering yourself.
2)do a regular 30miles a week, at an easy pace. Go and race a half marathon flat out, and afterwards, create some target pace zones afterwards.
Will build a base, and then start working you out to your designated time zones.
Without getting too heavy too early, your easy pace would be an absolute minimum of 1min 20 slower than your half marathon pace, all the way up to 2+mins slower.
A lot of runners worry running slower in training will make them lose pace in a race.
This doesn't happen as once or twice a week you run a hard session based on your own current pace zones...
i'll stop there for now, as we're all getting too excited with the anorakity of this!
when's your target half marathon?