I do feel for you. You can talk to Relate on your own, for advice, if that would help. It seems as if he has made his mind up? and despite you trying he does not want to get back with you? Would he agree to go to Relate as a couple?
It is heartbreaking when one person wants divorce, but it’s not mutual. You need to talk to your friends and family and get as much support as you can: and this will help you get through this. If there is definitely no way back, then as painful as it is you need to accept his decision. Accepting it will help you in the long run. It will be like a bereavement as you have lost something precious, but for your sanity you do need to accept it. Sorry, I cannot give you more positive advice. Look after yourself xx

Let him go. More often than not, when they fell out of love, it is because they found someone else.

I hate to agree with Unwanted but it is the truth. Women often leave their marriages because the husbands are messing up and they are utterly unhappy. Most men leave their marriages to be with someone else even if they had a great wife. Let him go. That's what I am doing with mine. Done with fighting for my marriage.