Hi,
Regarding your years in the Republic of Ireland for counting to pension purposes to the UK, you will need to discuss this with the International Pension Centre at the Department for Work and Pensions.
The agreement between both countries relate to social security but they will advise you on all aspects. Once you have spoken to them, you do also have the option of completing these years by paying by making voluntary National Insurance contributions that they may also advise you on.
International Pension Centre
Thank you.