PompeyPaul . . . which PA28 do you fly?
I fly a PA28-161 taper wing Warrior II which stalls at 50kts clean and 45kt full flaps.
The approach speeds for that (in knots) are:
Normal: 70kt then 65kt over the fence
Glide: 75kt then 65kt over the fence
Flapless: 75kt then 70kt over the fence
Maybe it was just a typo and you meant 80mph approach?
Getting back on thread, I usually add half the mean gust difference on blowy days ie 15G25 would add 5kts to my approach speed. As most PA28 taper-wing drivers will testify, you really need to nail the approach speed accurately otherwise you'll float into the next county
.