I presume you are not officially a charity? If you were then normally the Revenue will grant tax exemption.
Technically if you aren't a charity then yes, you do have to pay Corporation Tax on any surplus or "profits" the club makes each year. Clubs are caught by the same tax regime as companies. It would be profits for the year for the whole club though, not just the interest. If you use the interest to fund activities then likely the taxable profit is somewhat lower?
Are you sure the clb is actually receiving the interest gross from the bank / building society? They should be but many don't. It might already be taxed at source.
In any event, in practice the Revenue aren't really interested in taxing "not for profit" clubs. If you basically break even in funds every year they won't be interested in you. They may however question why a "not for profit" club has �15k in the bank. It's certainly an indicator that the club is more professional than that.
All of which hasn't really answered your question has it? Legally yes you should be at least registered for corporation tax. If you phone the Revenue they'll no doubt ask you to do so but they almost certainly won't care if you don't do it, especially as interest is likely to be much less in the next period sadly.