3 km closer?! wow! I was surprised to see that it got 'skipped' despite its coastal neighbour making the list but very well done for managing to be so accurate in your measurings!
Surprisingly, Monaco is further away than Ireland (and UK as well). It doesn't look like that on a standard world map, but it's more obvious on a globe. Ireland 9594 km / 5961 mi, UK 9627 km / 5982 mi, Monaco 9930 km / 6170 mi.