That was brilliantly written and a lot of thought went into it. I enjoyed it immensely. I loved how you wrote all the main characters, Geoff's character changed a lot but given the time between now and when the fic is set and given the circumstances of where his character is at that time meant that it was believable. I enjoyed how you wrote the characters as adults dealing with a situation as honestly and intensely as it should be written, Home and Away even has that trouble.
I was a little unsure about how Matilda said she'll be a bridesmaid at the wedding but in an earlier chapter she apologized for not turning up to the wedding as she had too much on. Although not necessarily a mistake if it was written in that she missed the wedding even though she was going to be a bridesmaid maybe you could have added something more to it, like Belle's feelings about her bridesmaid and one of her best friend's not being there.
Why is Vinnie back? Although there was that Patterson-Baker-Patterson joke, I didn't feel that Vinnie being back added anything to the story. I guess you just had it to show that time passes and things happen in that time. I guess it is probably because Vinnie is my favourite character ever and to have his return be small is upsetting. Probably my problem more than it is yours. Perhaps if you added a sub-plot or a conversation between Vinnie and Aden about Vinnie living a double life for a time and relating it to Aden not being true to himself could have made it work.
I did like the ending and how the characters loved each other so much that they will be willing to let each other go is a brilliant way to end things. I loved how you left it up in the air for Aden to return to Geoff, I feel a lot of readers missed the point and it was an ending to Belle and Aden's relationship. It's in the title, they can't go back to what they had and because of this they had to move on. It was a brilliant choice of title too. Not necessarily a brilliant song but it did work well with the story.
All in all, it was a brilliant read. A couple of things to think about in the future but you are a terrific writer and I am looking forward to reading your work in future.
Edit:
I was reading the wrong page it turns out the readers do understand the ending. My mistake guys