OK, I think I have sussed it so I have marked this thread solved
I will post where I have everything as the WAVES installer seems to put everything in the wrong place and with the recent offer I am sure others will come unstuck
To get the VST3 versions working this is where you need to put everything:
Find where the WAVES installer has put the plugins - in my case i was: "C:\Program Files (x86)\Waves"
In this folder is a folder called: "Plug-Ins V9"
You need to put a copy of this whole folder here: "C:\Program Files\Common Files\VST3"
In this folder you need to have the file: "WaveShell-VST3 9.3_x64.vst3"
If you don't have this file in your VST3 folder you can get it from the original WAVES install folder - which in my case was: "C:\Program Files (x86)\Waves"
In the "Waves" folder is a folder called "Waveshells" and in here you will find the file "WaveShell-VST3 9.3_x64.vst3", which you can copy and put in the "C:\Program Files\Common Files\VST3" folder
et voila!
Phew! - a bit of trial and error and some pointers from SIMPLEMANZ and SCOOK but I got there
I hope this helps someone else as I read about lots of problems and people were uninstalling, deleting registry items etc.
But I think moving a few folders and files around should save you from a bad WAVES installer