Some Irish pundits have asked why UK media has not made more of fact that Ireland has had, per capita, roughly half as many deaths as UK, claiming it was because Ireland went into lockdown earlier.

Maybe. But Northern Ireland followed UK lockdown rules and has seen a similar number of deaths per person as Ireland. Both are on a lightly populated island. Neither has a London or is a massive hub for international travel. All that might matter more than date of lockdown.