[lordmauve]

What we call cornflour in British English, and cornstarch in US English, is flour heavily processed to remove everything except starch, giving a flavourless thickener.

If you use wheat flour you will change the flavour and also add a slight graininess as the flour grains don't completely homogenise.

[duskwuff]

But watch out - "corn flour" in the US is unprocessed finely ground corn - like cornmeal, but less coarse. Not a substitute for corn starch.