the mount command is on the client side and doesn't control what the server allows.
you need to set up the share on the server so that anyone in a particular group ("valid users = groupname") can connect to the share, and then force the connection to be as user henry ("force user = henry"), regardless of what username/password they actually logged in with.
on ubuntu, as on debian, henry probably already has his own dedicated group (adduser on debian defaults to making a group for each user), but don't use that, unless you want everyone in that group to have access to all of henry's files rather than just those in the share.
e.g. make a unix (or ldap or Active Directory) group called "henry-share-g", and add anyone who needs access to the share to that group.
then configure the share in samba to set the permissions so that files are created RW by user & group, and directories are created RWX by user & group AND setgid (so that new files/dirs are created with group 'henry-share-g').
e.g. something like this:
path = /home/henry
force security mode = 0664
force directory security mode = 2775
force create mode = 0664
force directory mode = 2775
read only = No
browseable = Yes
force user = henry
force group = henry-share-g
valid users = +henry-share-g
this example makes the files and directories world-readable as well as RW by user & group. if you don't want that, then use 0660 for files and 2770 for directories.
BTW, the above is roughly what i do on my samba server at work whenever one of the professors wants a group share for everyone in his research group to be able to use.
the only real difference is that i don't use an existing user account. I create a dedicated user in AD for the share as well as a dedicated group, because there needs to be a separation between the prof's personal files and his/her research group's files. i also set a quota for that user & group, which is separate from the user's personal quota. i.e. i'd create and use something like "henry-share-u" rather than use the existing "henry" account.