As said take the points and fine. Theres no point arguing when you've been zapped by a GATSO or mobile camera the courts look at it as they dont lie like people do If it was an estimated speed by a copper sat in a car or on bike then id say argue away and you probley would get away with it but as said speed cameras dont lie thatS the way the court will see it and you'll probley end up with a bigger fine if you go to court over it