Fuse trips on spin cycle

Hello Gill. Unfortunately this is one of the faults that is extremely difficult if not impossible to diagnose without proper specialist equipment. However, if it only trips on the spin it could be something like a wire chafing and touching something when the drum bounces around. Check out my article here Tripping electrics

so unless you can see something that may be catching on the metal casing when the drum bounces around, or unless the motor is sparking excessively (which is another possible explanation) there's little you can do except to get an engineer.