Momo95, where in the UK have you been looking? Can't speak for England or Wales, but Scottish universities do accept and understand the Irish Leaving Certificate. Certainly Glasgow and Strathclyde (both have very good aeronautical or aeromechanical engineering courses) accept students with Irish qualifications, although you would need an A at both Maths and Physics, with a minimum of AAAB (Strathclyde) or AAAA (Glasgow) (Glasgow will possibly accept AAABB if either of Maths or Physics is a B, although the other must be an A). Perhaps the foundation year is being offered because of the B grades in both subjects? For Scottish applicants applying with highers, they'd make anyone with B's in Maths and Physics do advanced highers before accepting them, or a foundation course. I'd imagine it'd be the same with the ILC.
*Edited to stress that those are minimum requirements and don't guarantee a place, particularly if they can fill the course with students with 5 or 6 A grades.
As far as comparing ILC to A level, one ILC exam counts as 2/3 of an A level, according to the National Qualifications Authority of Ireland.
Incidentally, as an Irish citizen, you also wouldn't pay any fees north of the border.
Best of luck.
