You can access your goods when ever you like. You supply the padlock to your container therefore you control who has access to your goods.
They most certainly are. The yard is covered by 24 hour recorded CCTV. Also every container has a lock box fitted under which you lock your padlock.
You can store what you like as long as
a; It's legal and
b; It doesn't include food or perishable goods, gas bottles or flammable liquids.