Rated 3 out of 5 stars

Thanks again
The odd thing is it doesn't now, so I'll paly around with it a little a let you know.
Just FYI, I initially tried the regular function in thunderbird, I wrote a text signature and ticked the box in account settings. It worked fine, but inserted it in every email. I then downloaded your add-on and it took me a while to understand that you had to write something in the signature box, tick the add signature from file box and that it would only work then.
Now to try and answer your question, I ticked the insert text signature box again, and it does the same as with add signature, the text appears as a continuous line. The only other problem that I have is that I can't get thunderbird to forget the file path (I had also tried to insert a signature from file, saved as a txt document). Although I have removed the file from its location the path remains in the address line, even when I manually delete it. On closing account settings and reopening it, it reappears in the box.
Thank you, I will let you know if I find a way out of it.

This review is for a previous version of the add-on (0.2).  This user has other reviews of this add-on.

You could try to open about:config (http://kb.mozillazine.org/About:config), find your path and remove it there.