I got a prompt reply from support after their holiday which suggested changing the variable in skin1/customer/top_menu.tpl from $speed_bar[sb].title to $sb_title and prefacing the table cell with some code so that it would now read:
{eval var=$speed_bar[sb].title assign="sb_title"}
<td>{include file="customer/tab.tpl" tab_title="
`$sb_title`"}</td>
Then replacing the names on the Speed Bar Management page with a language variable such as $lng.lbl_home which you can then define in the Language admin.
I haven't had a chance to test this yet as I have been busy elsewhere but it sounds logical. I'm also not sure what the form is on repeating support advice in the forums, so if this is out of order please delete, admins.
The other question I had apparently involved mysql commands to update a table (which sound somewhat intimidating but don't seem too involved).
Added: Just to mention that the first solution works fine (remember you must put the curly brackets around the language variable in the Speedbar Management interface).