@marsaday
You are in a state of financial innocence as I was 30 years ago when I had such shares.
Firstly, shares in a private company are not readily tradeable. They certainly are not what Davy and other brokers normally deal in. You have to find an interested buyer (likely an existing shareholder) and then have the deal approved by the board of that private company.
The Old Kerry Co-Op shares were private company shares. They only had a nominal value, e.g. £1.
Each of these were originally valued during the 1986 launch of Kerry Group plc at around 10 times a Kerry Group share, then nominally 10p.
Today with the plc shares worth much more, the Co-Op shares would also rationally be worth much more.
The pre-Christmas deal between the Kerry Group plc and its major shareholder, Kerry Co-Op, has converted these old Co-Op shares into a mix of Kerry Group plc shares plus shares in a new entity Kerry Dairy Ireland. I think it's going to work out that 85% of the value of your old Kerry Co-Op shares would be converted into Kerry Group plc shares and 15% would be as shares in the new Kerry dairy entity. I am not sure if you can sell your shareholding in the Kerry Dairy entity if you plead non-involvement in dairy farming, e.g. if your Kerry Co-Op shares were inherited. If you do it may have to be to another Kerry dairy shareholder.
That's the basic position. To go any further you need to consult with someone well-versed in company practice, shares transfer, the Kerry Co-Op shareout referred to above and the tax and other implications of your situation. That is why I recommend a Co Kerry accountant because there are thousands of people like you in Co Kerry and the local accountants will be fully up to speed with both the situation, your options, tax aspects and so on.
Now, all I can say beyond this is to try to get an accountant who is trustworthy to you and let him/her elucidate on the position you hold. I could understand it if you felt the need to get more than one accountant's opinion on all this before you decide. It's a big decision so take your time.
Hoping it all works out.