I have successfully perfected a solution to recover data from AVHD files in a broken snapshot chain even if you do not have the parent vhd or you are missing avhd files.
A quick point to note: NEVER USE HYPER-V SNAPSHOTS IN A PRODUCTION ENVIRONMENT. Only use them for testing purposes.
If anyone needs help recovering data from broken snapshot chains they can get in touch with me via sean.ofarrell@ergogroup.ie and we can take it from there.