It should be noted that the Scriptures do not record the specific place to which Enoch was taken--only that he was taken.
For Elijah, he was taken up to heaven. However, the word heaven is used to refer to different things, namely the sky, the domain of the stars, and the dwelling place of God. It seems that Elijah arose into the sky, specifically. Wherever else he may have gone, we cannot be sure.
Thus, when Jesus says that no man has ascended into heaven, it seems that He is referring to heaven as the dwelling place of God and that Elijah must now, then, have gone there.
The story of the rich man and Lazarus (Luke 16) identifies a place of the dead referred to as "Abraham's Bosom". In this place, the rich man, who was in a place of torment, could see Lazarus and Abraham. This does not appear to be the dwelling place of God. On the Cross, Jesus referred to a place called Paradise, where the penitent thief would soon be with Jesus.
A common understanding, then, is that there was a place of paradise for the Old Testament saints, distinct from the dwelling place of God which we call heaven. This appears to be a place of waiting until the penalty for sins was paid, as it says in the last part of Romans 3:25
...This was to demonstrate His righteousness, because in the forbearance of God He passed over the sins previously committed. Romans 3:25b NASB
After Jesus died, it is understood that Paradise was taken into Heaven, the dwelling place of God.
Thus, Jesus was correct in asserting at that time that no man had ever gone into heaven except for He Himself who came from heaven. Old Testament saints had gone to Paradise, but not Heaven.