Right, part 1 is the fully assembled caliper assembly, part #2 is the caliper carrier that bolts to the HUB carrier that is bolted to the strutt. Part 3 is the actual caliper, which is fastened to part 2 with parts 5. Part #2 compes complete with the sliding pins, which are apparently the parts that are worn and causing the noise. Ergo, if you replace part 2 on your car, you will cure the knocking noise.
I can't believe the garage suggested getting new parts manufactured, the caliper carrier is £30-40 ,
And yes the parts shown were for a V6. Any competant parts guy at a Fiat garage should be able to navigate to that screen on the parts CD.