Well gosh... I like Harp as well, so while I haven't brewed this yet, I just went ahead and took a first stab at designing a recipe for us. Keeping it nice and simple -- I think the real key would be to use English or Irish ingredients, and a clean malty lager yeast. So how does this sound?
Harp Clone Attempt
8 lb English Pilsner malt
0.5 lb cane sugar
0.75 oz Kent Goldings (5.5% alpha, 60 minutes)
Wyeast 2042 Danish Lager yeast
Make a big yeast starter in advance. Need to add salts to hit Dublin water -- this is very important. And then the pH won't be low enough so add some of that pH 5.2 stuff. Do a standard single infusion mash for at least 40 minutes at about 149 F, boil 90 minutes to minimize DMS, ferment at about 50 F for 2 weeks, lager at 30-something for 3 more weeks. Carbonate in the mid-range for the style. It's all good.
Someday I might brew this. So easy, yet so delicious. If you get to it first, let me know how it turns out. Good luck.