I have a copy of this Waltz in the book 'The Library of Piano Classics (2) which states that the opus no69 no 1 is posthumous. Is this likely to be the Fontana version. I have listened to a Fontana version on youtube which corresponds with the music I have but just wanted to be sure. Can anyone clarify this?

I have the ABRSM edition of Chopin Waltzes and in it the Ab waltz (posthumous) is definitely the Fontana edition -I remember somewhere on the internet I found a description of the differences in the Fontana edition. Unfortunately I am now completely unable to find the same document but if I do I'll post the link. One of the features of the Fontana edition is (I think) a crotchet rest for the right hand on the first beat of bar 7.
If you google this edgreenmusic.org/Articles/EdGreen_Chopin.pdf the pdf has the 1st 16 bars of the Fontana edition in it

My Paderewski edition has both versions:
the first is subtitled 'D'apres l'edition posthume de J Fontana'
and the second 'D'apres l'autographe varsovien'
so yes, your posthumous one will be the Fontana ed.

Enjoy playing it - I love this piece

Thank you for your replies - there is a crotchet rest in bar 7 in the version I have. It is a lovely piece which I will enjoy doing.