I solved this problem as follows.
I found the instructions on installing Thonny over an existing python installation
As I had been playing around with python I realised I had a number of python installations.
I removed all python installations and IDE's from my windows (including manually purging directories)
Installed 64 bit version of python
Installed 63 bit version of pywin32
Installed Thonny over the python installation above
Selected the above python installation as my interpreter.
No problems importing win32com
If there is a way to use win32com using the built in python interpreter please let me know.