Falling apart means too much liquid or too little binder, or both. In your case, I think it's mostly the binder.
Your description sounds similar to this recipe. The proportion of breadcrumbs to milk/cream is about the same, but notice that this recipe uses about 0.75kg meat and one large egg. You're using 1kg of meat and one egg (of unspecified size). My meatloaves uses to have problems with structural integrity until I understood that recipes (at least in the US, where I live) default to large eggs, not the medium I was using. For your meatballs, I would try adding another egg or upping the egg size (medium -> large or large -> extra-large).
I don't use dairy in cooking meat so I don't have direct experience with the breadcrumbs/cream part, but I noticed that the linked recipe says to let them soak for about 10 minutes, longer than you said you soaked yours. 2dl breadcrumbs aren't going to fully absorb 3dl cream but you want the breadcrumbs to absorb as much as they can, so try soaking them longer. Or if you're in a hurry, decrease the cream.
Finally, with meatballs (unlike meatloaf), you can adjust as you go. Start with just a few meatballs in the pan, and if they fall apart, adjust the mix before doing more by either adding some breadcrumbs (to soak up extra liquid) or adding some more egg. (It doesn't have to be a whole egg; lightly scramble an egg in a bowl and then you can decide how much to pour in.) Cook a few more, see how they do, and when you like the results, you can cook the rest.