I send stuff to the recycling centre all the time, Van costs €12, so isn't free but worth it to get rid of them. Rads are worthless, so you'd be lucky to get someone to take them off your hands.
The recycling centre in Dundalk (V&W recycling) takes scrap metal including radiators - the entry fee is 2 euro for private (i.e. not trade) customers.
I'm sure there may be other centres who accept them.