Assuming he's Irish, did he close all his accounts before he left? We kept one open in Ireland through years in the UK and occasionally sent money over to it - we just had to provide information about our address and tax status and there was no issue with it.
It is usually easy enough to keep accounts and update with a foreign address, but opening them as either a new or returning resident is incredibly difficult: I foolishly closed my UK bank accounts when I moved back to Ireland for a few years than had to jump through all manner of hoops on my return.
The easiest thing might be to use an existing account, if there is one, and speak to the bank about the implications of his current residence and tax status.