Um...I belive it's in the Butchers Shop,Or close to where it is.

goto tesco avoid security and nick the key from a bottle of milk i left for you ****
****ing ****ity ****

none of the above are right lol, ok you need to go to the cars and get the pink one
next go down the parking lot and go right until u find this little dip in theres a door
there and u can open it inside is a sledgehammer and some other stuff go to the very end
and there will be a key there pick it up (btw dont worry it doesnt take up any inventory
space) :) best thing to do is look on youtube hard to expplain in writing :p