I entered into a mutah marriage.
We mutually agreed that the relationship between us was over however he did not utter the phrase in Arabic to end the marriage. However it was clear that we would not be in a relationship any more by his choice.
There is still some time remaining on the original time period.
Can I conclude that the mutah is ended? Or is it still valid because he did not utter the correct phrase in Arabic?

The phrase does not need to be said in Arabic. As long as be clearly told you the remaining duration if the Mut’ah is over, then the Mut’ah ended. If you still have doubts about that (you don’t remember exactly what he said), then either wait till the duration expires, or ask him to end the remaining duration now.