Wow. Well it started out ok, building lots of fast paced tension and nerve wracking moments of ‘anything can happen’ then it starts going wrong. 

The higher the girls get, the lower the film goes. 
Things get more than predictable and a lot more unrealistic. 

Seems a shame, a waste of a good idea. Did the job for 10-15 minutes, but that’s it.

So I’ve spent some time thinking about this and although I really enjoyed it, I think the music carried the film. The music and Rami Malik. 
The story kept feeling like something was missing, something we weren’t being told. Or even we were just seeing one thread of a story which is a lot more complicated than we are being shown. 
It was enjoyable but with that something missing I couldn’t score it higher!

Not bad, took an unexpected turn at the end which I appreciated. 
Spall was funny enough, enjoyed some of his humour and delivery. 
Enjoyed it, laughed a few times and my wife enjoyed it too which is always a bonus!