Send the store an email or ring them. The more people that let them know that the spaces are too small, the quicker they will fix it.
Cars have definitely increased in width to improve the road stability. Some places now have wider spaces with a 'loop-line' between the parks to let dumb drivers know just where they should park in the spaces.
Ofcourse, more spaces means room for more shoppers, but if enough complain, the sooner it will be fixed... or potential customers will go elsewhere.
We now have a fairly new car and always park in the quieter section in the car parks, away from the 'I must park as close as possible to the shop or I might drop dead walking a few more paces' people. These lazy souls are also the ones that usually have little regard for other's pride and joy.