You can buy everything seen in the "upgrade/edit appearance" menu very easily.

First earn over 100.000 pounds in career mode then enter the "upgrade/edit appearance" menu. Now buy everything you can afford DO NOT CLICK ON DONE or you will lose your money. when all your money is spent press the B button to go back to the main menu and save your game. Now when you return to the "upgrade/edit appearance" menu you will have all you bought and still have your earnings. Repeat this to buy everything.