I am not a gamer so havent really any experience of your problem Dom, I have had a look around and everything seems to point to either something in your own network/modem/router settings or a server being down on your normal route.
Maybe your friend on your ISP is connecting on a different route or it may be a local problem nearer to you
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do you get the high pings on just the one game or on others too ?
If its on others then it sounds like your settings.
One thing I did see was trying altering your acceleration in graphics and sounds, that may have changed when you reinstalled after your format
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