I've owned and driven an unmapped then k-tec re-mapped 182 AND an unmapped then RS-Tuner mapped 172 and can honestly say its the best mod i've made to both.
Improves driveablity, sorts out the lumpy idle, increases low down torque making the car pull harder lower down the rev range and also improves mpg slightly!
If you're considering it, buy an RS-Tuner - Map you're car then sell it on. The cheapest and IMO best value for money way of noticeably improving the performance of your car.
If you go down the RS-Tuner route, excluding the cost of the unit your map will only cost ~£70.. which is a f'ckin bargain tbh!