[joglynne]

Ok I had no success with any thing I tried and ended up trawling the Mozilla beta forum for a solution. A member with a similar problem of a missing option had found a solution that I tried and found successful. So just in case it may come in useful to anyone else this is something to try.

Insert an icon from Customize Toolbars option in View on to the menu bar (I reinstalled ABP and used that icon) for some reason that prompts the add new tab button to appear at the right hand side of the Bookmarks Tool bar. Once you close the Customise box the add new tab thingy jumps across to the right of the last tab.

I hope anyone who needs to do this can follow what I did but if not feel free to PM me and I will attempt to talk you through.