Yep they're the ones Shoduchi.
In that case, thinking about it, perhaps it's due to the fact I'm only able to put one in, as the other side has a led numberplate light integrated with a reversing camera.. Which has always worked regardless.
Im wondering if, as it was only 1 LED light before, and the other side was a normal 'Festoon' bulb in the standard unit, there wasn't enough of a resistance discrepancy to throw a warning..? As I'm assuming the wiring for both lights are both on the same loom, does that make sense?