As Squeaks says, that porch looks quite shallow, so I'd position the top of my ladders to one side of the window, or just above it and have the feet resting on a Rojak ladder stopper.
My Rojak has holes drilled in the corners and I can use tent pegs to peg it into soft ground (a tip from this site).
If you wanted to be doubly safe, you could also tie the ladder off, using the wooden brackets that support the porch.
This advice may not be HSE acceptable, but common sense tells me I'd be safe.