Local and Domain NT user accounts

[Dave.Stevenson at durham.ac.uk]

At the moment I have a nice one-to-one mapping of
UNIX <-> NT domain user account   ( usernamemap is not used for one-to-many)

If I have a user with local accounts on several machines and a domain account (with same account 
names = their unix id -  but obviously different SID's)  what is the best way to ensure that they 
can access their files on both SAMBA shares and LOCAL NTFS disks from any of their accounts without 
compromising the privacy of their files?

Any thoughts or obvious solutions welcome, I can only think of clumsy ones.