I never cook for my freezer, the only things I have ever frozen are left over chilli, or spag Bol sauce, as a result lots of left overs get thrown away. The things is I don't know at what stage of cooking you fees things and so would worry about poisoning people (my cookings bad enough).
I am making a veg Lasagne at the weekend there will definitely be left overs can I freeze them once the whole Lasagne has been cooked or not?
yes - cool it in the fridge overnight so it goes nice and solid and will keep its shape when cut. Then slice into portions and wrap each portion in tinfoil before freezing. Defrost at room temp and then reheat either in microwave or in oven in a dish covered with foil (to prevent top getting burned as it reheats).