Because you have such a low mortgage on the Clare property, it would mean that you're going to pay a lot of the income in tax, and you'd be also subsidising the mortgage out of taxed income.
It would look better to sell, releasing about 220K. The buy a house in Cork with a mortgage, money is relatively cheap, and paying back mortgage can be a type of saving. Make it a well manageable mortgage. And then invest the 220K, maybe in a couple of city apartments that are yielding a high amount. No harm to have them on mortgages initially to get the interest relief of 75%. Then near retirement you'd have the mortgages paid off and the rent would become an income. If you buy in the right location you may have free accommodation for your college going kids.
Or if you can come up with better ideas for a return on the 220K all the better as being a landlord is not as easy as some people think. It brings a lot of headaches, but if you buy in a good location, with a high yield and it's well built than it's not so difficult. Better that the apartments are close to where you live.