Hi, welcome onboard 
Only real thing I regreat about not going SS was the Wheels and the Stance as I opted to stay on 16"s as they where less popular and it does sit abit arse high on the smaller wheels.
On a dyno day we found that the NP non SS cars made bit more than 135bhp and actually wasnt that far off the 160bhp, also on a day out driving with two other cars with varying bhp's I think you'd need around 20bhp+ extra than another car on long straights to really see a difference
I think unless you was coming from something else turbocharged with around the same kinda output then I think your be well happy with the standard car. Like all cars there always room for improvement its just a case of money 

thanks
Yeah I do like the ss wheels but there are nicer ones out there to buy that would be half the price. I quite like the petals anyway. Yeah they do sit rather high, coming from a lowered corsa anyway.
Really? Were they all consistently higher than 135? To be honest, bhp figures really don't bother me, it's how they drive that I'm more interested in and I think you're absolutely right, maybe if I was going from an evo to the abarth then the standard would feel slow but from my corsa I'm sure it'll feel more than quick enough.
Although I'm sure it won't stay standard for very long