Blue Tits Trapped

Hello, 

I am in urgent need of some advice in relation to a Blue Tit Nest.

The nest initially appeared to be in a small alcove within my porch roof however I have some concerns the nest has fallen down a small almost tunnel like space and come to rear behind a facia board to a dead space above a window. With the nest itself potentially blocking the access point to the tunnel? 

Over the past few days an adult bluetit appeared to be regularly going in and out to to tend to chicks that I can hear from behind the facia board. This morning however can I see a dead bird lay on the grill within the facia board. The adult bluetit is still about but appears somewhat distressed as its singing a lot and flying around from tree to nest to tree to nest in very quick succession. 

I am concerned the chicks are stuck and am a bit of a loss what to do now. I am in no way an expert but do know that in the best interests of the chicks you shouldn't where possible interfere with a nest. A principle enshrined with the countryside act. However, at the same time I don't want to do nothing if the chicks are stuck.

Any advice you can give would be really appreciative? Should I try and create a hole within the facia board to allow the chicks to escape or do I just let nature take its course and see what happens?

Please find attached some photos and a video. First photo is where the nest initially was the next is where the nest appears to be now. It's to the left of the first photo be a meter.

Thank you for your time. 

Dan