Marking a product as 'Made in England' if it isn't, is quite a serious offence in the U.K.
Even implying or suggesting it's made here, when it isn't, can be an offence!
A major clothing chain was heavily fined for selling a clothing range that 'suggested' it was Italian, when it was in fact made in India or somesuch!
There are numerous firms forging chisels here in the U.K, and most of them are pretty good, but If Stanley are among them I can only assume thst the work is outsourced since the old Stanley works in Sheffield stood empty last time I was there! Do they have another plant?
Is it feasible that Stanley manufacture them in the U.K. for the European market, and South America for the U.S. market? Quite a few firms do something similar!
Personally, I'd probably just buy a Robert Sorby, or Henry Taylor, or Ashley Iles chisel that I know is British made. Or if availability is better, a German made Kirschen or a Swiss Pfeil!