Frank, as somebody who worked in the HSE I can categorically say that the amount of people who want addition of previous service either from another public service body or the civil service or even a Health Board is phenomenal. Worse again many of these wait until just before retirement or just on retirement to inform the Personnel section of the previous service. This service has to be verified by the other bodies. Very often their records are consigned to some obscure storage agency and often there is difficulty in obtaining hard proof of the time you spent there. The obligation is on you to provide such records when you changed employment.
Now, if in past years you did provide the HSE with proof of your previous service and supplied letters from your previous employer/section, then disgracefully the HSE is at fault.