Hi summergirl
OK, I think I'm right in my thinking. You travel on 2nd October, so if you started your insurance cover from that date you would be covered for 12 months from 2nd October onwards, which is fair enough.
However, imagine now, you've paid for e.g. the hotel, the flight and say tomorrow you have some sort of disaster (for example you fall ill) and are not able to travel. As your insurance cover doesn't commence until 2nd October you will not be covered for your cancellation costs etc.
However, if you commence your insurance from now, then you will be covered should anything unfortunate happen which will prevent you from travelling.
Hope that makes sense. Please correct me if I'm wrong guys.