When I read the following comments I know there's a message being sent;
"Two months ago his partner of seven years moved out of their flat with no warning she said she felt smothered."
"she said they had nothing in common."
"she just needs space"
"there was a text message on it sent from her to another man ...inviting him back to her flat".
it's apparent to me that she has moved on and that counselling would be a waste. It's difficult for most people to end a relationship gracefully so they try to have it both ways to ease the pain, which always makes things worse in the end. It doesn't sound to me as if he needs to get to the bottom of this, she already has.
I would advise him to let her go and move on. If she feels differently ,she will not allow that to happen but if she does agree to move on he'll know the answer.