If I were you, I would request a P21 balancing statement.
Just to be clear, you will not receive a refund of the PRSI paid.
I am assuming that you are single, or if married, have separate tax assessments.
If so, you have 3660 euro tax credits for the year, you will have used 1/6 of these, ( 1/12 per month for Jan and Feb). Therefore you have 3050 unused tax credits.
If you paid less than 3050 tax, you should get all of it back.
I dont know how this affects your UK tax return.