I'm only being realistic in what I have said in my posts, in regards to the presumption that it was indeed bought for less than £250.
Gigabyte will indeed know how much was paid for the card due to requiring the original invoice to deal with the rma process(whether the op want's to divulge this information or not

).
In which case if indeed it's one of the 'cheap' ones, he's better taking the replacement.
No matter what we all say or think what the card should be replaced with, it's entirely at the discretion of Gigabyte to hand out a card of greater value, which I doubt they will, again this is in regards to being a 'cheap' one.
There is no harm in trying though, just remember to be very polite as you'll get nowhere being arrogant or demanding with them.