My mothers Mini Cooper 1.6. Literally struggles in 2nd to go up some hills.
Maybe there was something wrong with it then ...I know you said there wasn't, but are you sure?
I used to drive a Cooper from time to time, and while it was no speed demon, it did not struggle to go up hills in second ...well not unless you were to trying to pull away from zero in 2nd up a hill anyway (which is silly) ...or perhaps if you were to trying to pull a 24' caravan up it.
Now uncomfortable and lacking space I will grant you, and it didn't have as much go as you would hope, but it was plenty quick enough for ordinary, day to day driving. I used to drive a 4.4l V8 remember, so it's not as if I was wowed by the awsome 120bhp because I was used to 60bhp. I'm just being realistic. The Cooper is fine, it's not fast, but it's not really 'slow' either, not in the same way a Matiz or an Agila is.