Hi, Best way is to make a copy of your current profile folder, and then set up the new sync in the about:accounts page.

Currently there is no functionality for remote wipe, but you can start a new account for future syncing to that device.

I hope this helps. Sync your Firefox bookmarks, history, passwords and more

Thank you for your help. It would appear that I didn't have to back up the folder. I didn't have an account at all so upgrading to the latest Firefox, creating an account and syncing seem to have worked (at least with regard to my Bookmarks which is the most important thing for me). I can't be sure that this has stopped my information going to the tablet, of course, but fingers crossed. Much appreciated.

Glad to hear this Myrtle, thank you for using sync! If you have any other questions feel free to check out the forum again!