My tuppenceworth, I’m buying notional service but it very much depends on individual circumstances.
There are a number of issues and assumptions that you will have to take into consideration.
What age do you plan to retire?
Are your 12 years of work so far in Ireland all pensionable in the public service ? As stated above, ensure firstly that all your public service is ‘reckonable’ (credited for pension purposes).
Public servants have different rules applying to their retirement largely depending on when they started work. You need to be sure of the conditions applying to you.
Your public service pension will be integrated with the State Pension (I.e. in effect the State Pension amount is deducted from your Public Service pension). So far many people, (low salaries / fewer pension years) it won’t make sense to ‘buy years’ - which can be expensive.
If I were you, I’d start by estimating your Irish State Pension - complicated by plans to introduce new calculation methods (and in your circumstances, possibly overseas credits).
When you have a good idea of your potential State Pension, then do some calculations, based on the integration of this with your potential Public Service pension.
When that is worked out, you can estimate how long you hope to live !
Good Luck !