Suggestions for Parts Needed

Hi I'm trying to design a circuit which seems simple enough in theory but I have no idea what kind of parts I would need for it.

Basically the circuit will provide power to a premanufactured LED unit from the mains, unless the LED unit is removed from its fitting. It would then be able to be used as a torch.

So this means there needs to be contacts which supply a path for the electricity when the LED unit is slotted into the fitting. Also the circuit must allow a small battery to power the LED unit when switched on as a torch.

I'm on a work placement and this design could end up as part of the product range, so I want to be careful that any safety components are included also. Any suggestions welcome.

so

this means there needs to be contacts which supply a path for the electricity when the LED unit is slotted into the fitting. Also the circuit must allow a small battery to power the LED unit when switched on as a torch