They are simply 'international' GCSEs. I don't see why they wouldn't be accepted, the only 'sponsorhip' (they aren't any true sponsorships in this country anymore) schemes would likely be more concerned with further education such as A levels. For example the 'mentored' (apart from CTC the closest to an airline running sponsorships) schemes at OAT require and A level in a science based subject and maths preferably. CTC just require 2 A levels of any subject.
As far as GCSEs go, you definitely won't have a qualification recognition problem with anyone just because you took an iGCSE
