Somehow, probably editing my sources.list(s) in response to the recent jessie updates removal, I have managed to break the apt update/upgrade process:

After searching I've tried various suggested fixes such as 

apt-get -f install 

apt-get clean

apt-get autoclean

apt-get autoremove

apt-get dist-upgrade

dpkg --configure -a

and so on but all to no  avail.

There is some info on my system below.

Thanks in advance,

Richard.

------------------------------

-------------------------------

--------------------------------

My /etc/apt/sources.list 

In sources.list.d/ there is

certbot.list