I have just did this myself. Like the ops say fill out the NI38 for this, (there is abit to fill out on it), you will be able to claim class-2 contributions, for the amount of time you have been working in Ireland, which comes to around £158 to £160 per year. So this is a no brainer!!
Now this can and will take 20 weeks, so does take a long time. Also i phoned them on the number that came with the letter and asked how many more years, can i claim after this to get a full UK pension. I`m 55 and was told another 6 years would do that for a full UK pension.
Also if you have old pensions from different companies in the UK they can be hard to trace, i have found 4 so far from the UK gov tracing web page, and doing some of my own investigations. Also you can google "request for contracted-out information" and again write off to HMRC to tell you what pensions you may have lost if you contracted out in the early days.
Good luck and hope that helps a little.