I have created a simple html page stored locally with quick links to my favorite Tor services and set it as my home page for Tor Browser, but it seems to be overridden with the default torproject.org page every time I restart Tor. Is this a 'security' measure or have I missed something?
The Tor Browser Bundle overwrites your local files in every update. This is intentional.
I recommend to save your personal homepage in a directory outside of TBB's directory and make a link. So you only have to renew the link. Another possibility is to import the file on each update.