12st would still put you above a BMI of 22.5 for average height, 15st is well into the obease end of the scale! Bear in mind roadies are statisticaly going to be at the lighter end of the scale, buying lightweight wheels if your not light yourself is going to be both pointless and probbaly expensive.
Shimano R-550, not super light (marginaly better than askiums, especialy the rims being lighter which is where it matters for feel at the expense of heavy hubs) but are cheep, and seem to last pretty well with a none too subtle 15st me*!
*I had to add 1/3 turn to the rear spokes to stop them rubbing when I was fit a few years back, despite weighing more now I dont have that kind of power anymore 🙁