Hi, I no I'm posting lots of questions so I'm sorry, 

Im a bit confused because stitch was neutered a good 2 months ago now and he has started humming and buzzing and getting exited and humpy with the girl I'm trying to bond him with, has anyone heard of this happening?

I thought there is a chance he's just excited and in love

What do you mean by humming and buzzing? The humping may be a display of dominance.

He is probably humping to show he is the dominant one, I'm not sure about humming and buzzing? The only noise mine has ever made is honking and grunting (he sounds like an angry goose) when he is really mad at me, like if I try to put him in his carrier.

could it be tooth purrs? Rabbits can sometimes grind their teeth together when they are happy and content and it can feel like small vibrations

No its more like the noise he used to make when he would run circles round me before he was neutered, it's only when he cant get to her and whennhencannhenjust humps loads

BB's bunny Jack used to hump quite a lot even though he was neutered. It turned out to be a bladder problem that was irritated and made him behave that way (at least when he was older. Not sure it was true for him at a younger age. But he was always a humper.)
You may want to have a follow-up exam by the vet just to make sure the procedure healed as planned and he is well.

Otherwise, it's his assertion that he is the dominant one, and the noises are probably his excitement at being bonded. Hormones recede, and he is now sterile, but they don't necessarily make him devoid of affection, aggression or emotion.

Jackson still makes his humming buzz noise when he is hopeful that Coco will let him mount her. She has never allowed it in 3 years, but I think of it as his "hopeful"noise.

Both of mine make buzzing sounds when food is involved, so it's not only a hormonal behavior. Otto will also occasionally circle Hannah while making a very quiet buzzing and I think it's just his way of saying "I love you".

And neutered buns definitely hump! It's more to show dominance and communicate than anything else,