How do I undo pull-cord housing on Mountfield Omega 32 Lawnmower?

I am trying to replace the pull-cord for my Mountfield Omega 32 petrol lawn mower.

I have removed the plastic casing from the top of the pull-cord housing, but cannot identify what tool is required to undo the three screws to access the starter cord housing.

Please can anyone help with suggestions - I have tried allen keys and wonder if the screws are in fact hex?

Thanks