[ferzul]

tire vs tyre - apparently “tire” is older, but when pneumatic tyres became a thing, the spelling “tyre” caught on in England. So that's not an option.

kerb vs curb (n) - again, curb is older, but somehow a spelling error^W varient caught on in England. In this case, it is unfortunate since Scottish people allegedly pronounce “curb” but write “kerb” (they pronounce ur like u+r and er like e+r, not as a single sound). So this one is not just not an option, it's actively hostile to many British peoplee

-or vs -our: unless you will spell governour and use other like spellings, you have no historical leg to stand on so you might as well allow both variants.

program is the older spelling, programme is preferred by those who are jealous of the French.

I never understood the logic of swapping -re to -er in theatre, centre tho. I mean, why only -re but not -le? why don't Americans tickel and cuddel? Surely the logic is the same. So I think you can mount your high horse here.