As I said in a previous message on other topic, in Europe (except UK 240VAC) the standard mains voltage is 230VAC, so if possible please put this tap for export models too.
If the amp does not have 230V tap, and we have to use 220V or 240V tap we won't be running the amp in the original designed voltage. The safe thing is to put it on 240V, but that means having almost 4.5% less voltage on B+, wich can be like 23Vdc for 500Vdc B+. If the amp is setted with even a lower B+ (compared to the original CCV) to accept the JJ EL34 instead of =C= SED 34, let's say 485Vdc for example, then the difference with the original ones can be 30-40Vdc on B+, wich can lead to different response and sound. Don't know if it would be too much noticeable... but I just want to tell this for you to consider. I'm sure Mark, Dave and co. knows all this, but as official 230VAC mains is "relatively" new, I preffer to let you know.