A manufacturer's warranty is entirely separate to your statutory rights. It's a 'gift' from the manufacturer and, as such, can be as limited or as generous as the manufacturer pleases. (For example, it's perfectly lawful for a manufacturer to offer a warranty which is only valid if you deliver the defective item back to the factory in China in person, on the third Tuesday after a full moon, while stark naked, standing on your hands and singing the Lithuanian national anthem backwards. It might be odd but it's not illegal!).
However it's common practice for a manufacturer to rule that the warranty on a replacement item is only valid to the same date upon which the original warranty was valid.
Anyway, unless you've mis-typed your dates, the second iron would still be out of warranty anyway. (14 months have passed since March 2016).