I have the 'underfloor storage package' and quite frankly it isn''t worth the money, When the weather improves I'll be looking at the options removing it gives. There will be more space without it but I still don't think it will be possible to lower the boot floor because of the battery.
I am finding the lack of stowage space to one of the major failings of the car - compared with the current Polo that we have too it is dire - the glove box is tiny, the under seat box is tiny, the boot is tiny. On the Polo there is a seperate compartment in the glove box for the car handbook and with that tucked away there is twice as much room as in the A1. The underfloor area of the boot on the Polo is fully trimmed, unlike the A1, it has a spare wheel and you can drop the floor to the lower position.