Problem is the new corsa and fiesta both likely to have the same power as the GTI, those of you who say the gti doesn't compete against them are kidding yourselfs, both likely to be 9k cheaper:
As I've said above, power isn't the only factor to consider when thinking about what makes vehicles 'competitors'. Both the Corsa and Fiesta are superminis, the golf is a family hatch. That in itself not only brings practicality into the mix, but also the image of the vehicles. Now of course, those looking at the GTI as a performance car might also consider the hot Corsa and Fiesta models, but those who are looking at the GTI as a family car with performance ability will not be interested in the limited practicality of the smaller superminis. Likewise those who are attracted to the class and quality of GTI badge are not likely to be seduced by a Fiesta or Corsa.
And again, as I said above. There is also the VW Polo GTI, which
does compete with the Corsa and Fiesta offerings.
It's not inconceivable that someone considering a Golf GTI might also look at Corsa VXRs and Fiesta STs (I myself considered a MINI Cooper S JCW), but being realistic the direct competitors to the Golf from both the Vauxhall and Ford stables are the Astra and Focus respectively.