make sure there isn't a leak in any of the hoses.
A month after I got my Sporting I noticed a minute hole in one of the heater hoses that had had some sort of tape put over it. I took it back to the garage under warranty and spent a month in a bog standard corsa

while they waited for the replacemnt hose to arrive from Fiat.
I think this may be a common complaint as the part wasn't available anywhere...eventually being shipped from Italy, after one that was supposed to arrive from Poland dissapeared!!!
My car was over heating really quickly as well...and running out of water at an astonishing rate! Check to see if you can see where water is spraying out of a hose.
It might not be this, but just thought I would pass onmy experience!
Drive it like you stole it!