It could have been just about any fish that swims, the only things i haven't caught on bread are perch & pike.

Next to worms, bread is the most universal bait ever invented. I have even caught perch and pike on it - brown bread in particular.

If I think back I must have caught well over 50 species in my life on bread.

Why don't you fish it and see what you get?

You say never stocked and rarely fished, well, something is obviously in there.

Out of interest; why is it your favourite lake?

it's my favourite lake, because i caught my frist rudd (could it be the rudd?) and my frist in it.

Someone told me it mite be carp, could it? are they only stocked fish in Ireland

? 

Now it becomes a little clearer.

As far as I know, carp are not indigenous to Ireland, likely they are rudd!

As Fred says, very likely to be rudd.

I fish lots of places where people feed ducks with bread (park lakes, canals, etc). Bread is nearly always the best bait in these places.  If fishing is allowed, give it a go max. Light float tackle, set shallow (12" deep) and you should have them crawling up the rod.