Belgian and Irish/UK taxes might be quite different and services provided by state as well.
I used to be engineer in France, making much less money than as captain now.
But, if I messed up in my engineer job, the company lost one day of computer productivity .
Now, if I mess up, I can kill up to 189 pax + 6 crew + 1 tool worth around 60 millions $ !
That's quite a huge difference that can justify a payrise in my opinion.