Winko, grit (6mm) is by far the best medium for mixing with compost to give improved drainage. However, it is heavy. If you are going to move the pots arouns a lot this might be something for you to take into consideration. We take plants to shows all around Scotland in clay pots up to 10" in diameter using grit as drainage. Above that size the are too heavy for me.
Polystyrene balls, rather than lumps would make for a lighter compost but I just don't fancy it.

I wouldn't use bubblewrap, except to use as a liner between the compost as the pot if you want to keep the plant roots insulated - I have used the polystyrene boxes that bedding comes supplied in, broken up and placed in the bottom of pots as a layer where weight is an important issue. Otherwise, if you want good drainage, buy Perlite or vermiculite mixed with the compost, both of which I've also used to keep the weight of pots down.

I use the polystyrene in the bottom of pots too,and keep all the large pieces used for packing large goods,in the loft for future use...We yorkshire folk never throw "owt" away...and best to add grit as suggested for drainage...