OK - based on various sources across the web I've deleted or cleared most (if not all of the following):
~/Library/Caches/com.apple.Safari
~/Library/Caches/com.apple.WebKit*
~/Library/Caches/com.apple.Safari
~/Library/Caches/com.apple.WebKit
~/Library/Caches/com.apple.WebKit.Networking
~/Library/Caches/com.apple.WebKit.Networking
~/Library/Safari/LocalStorage
~/Library/Safari/Databases
~/Library/Safari/Metadata Cache
~/Library/Preferences/com.apple.Safari.plist
~/Library/Preferences/com.apple.Safari.RSS.plist (if it exists)
~/Library/Preferences/com.apple.Safari.SafeBrowsing.plist (if it exists)
~/Library/Group Containers/<random>.com.apple.Safari/WebsiteData
~/Library/Group Containers/<random>.com.apple.Safari/WebsiteDataStore
~/Library/Group Containers/<random>.com.apple.Safari/WebKitWebsiteData
~/Library/Group Containers/<random>.com.apple.WebKit/WebsiteData
~/Library/Group Containers/<random>.com.apple.WebKit/WebsiteDataStore
~/Library/Group Containers/<random>.com.apple.WebKit/WebKitWebsiteData
/Library/WebKit/WebsiteData
/Library/WebKit/NetworkProcess
/Library/WebKit/WebProcess
/Library/WebKit/Storage
/Library/WebKit/GPU
~/Library/Group Containers/Library/Caches
~/Library/Group Containers/Library/WebKit
~/Library/Group Containers/Library/WebsiteData
~/Library/Group Containers/Library/Safari
I've also found this tutorial on how to reinstall your OS which say will also reinstall Safari - don't know how safe it is though... Link here...