Hi Peter, with your help, I figured this out. I remembered way back that I started having this problem with training a CNN when the PyTorch  1.2.0 was introduced. Anyway I came across a line of code which seemed to implement the appropriate version of Torch and Torchvision to install in my case on my older Dell Optiplex desktop, which was PyTorch 1.1.0. The code is as follows:
(tflow) clived@clived-OptiPlex-760:~$ conda install pytorch-cpu torchvision-cpu -c pytorch.
I ran this in my tflow env (Python 3.6) and in the Python environment (Python 3.7) as you suggested, and in both of these situations, my training a CNN model worked fine.
Glad that this has been resolved, as I had this in my head for like the last two weeks.
Thank you
Clive