I would get the ashes back, but so I could bury their remains, not necessarily keep them.
I haven't had to do this with any large pets at this point in my life, but I have had cremation services done for a few rats and a sugar glider. The rats I asked to be cremated because they were with me while I was in college. When they passed, I wanted them to be buried at home, but that was a few states away at the time.
We are keeping the ashes of our sugar glider for the time being. He has a nice box that we keep on a shelf. Eventually, he will be buried also, but his best friend/"brother" suggie is still with us, and we want them to be together whenever that time comes.
ETA: I have had to move away from so many houses where pets (or their ashes) were buried. It is sad, I admit. But at the same time, once they're buried... it's like they are no longer there. That at that point they are finally free and don't have to be tied to that body/ashes anymore, and it doesn't matter where I go.
That said, that is the reason we've kept Penn's ashes (sugar glider) for now. We don't want to bury him and then have to move away... and then not be able to put Teller with him in the future. Once they are together, though, they will always be together, wherever they are or where we are.
I hope that makes sense...