SOLVED
So this morning i updated to the newer version of PM+, same problem with thumbnails. I then played around with the following Tabs Under Preferences
1: Reduced the Render Cache Size to 1024 MB under Preferences.
2: I unchecked all the tick marks under the Preview Tab, except for Enlarge Photosto fit previews and slide slow.
3: Under Contact Sheet - Thumbnails i enlarged the default size for thumbnails, and selected Generate high quality thumbnails
4:Under Launching I changed to Edit The RAW Photo
5:IPTC /XMP When Viewing Photos in RAW +JPG I chnaged to RAW File
6: For JPGs with Multiple IPTC and/or XMP records a chnaged to Read/update the first one - here it asked me to restart PM+
Not sure which one did the trick, but the thumbnails are back to being blistering fast