Found this one quite difficult going - really felt more like an episode of 'Morse' than some thing designed for film - Morse lovers are usually glued to their TV set with half a sherry - not the types to get themselves out to see a good film (I'm stereotyping, I know, but that doesn't mean it's not true ...).
The Britishness of it, though, will weigh it down with problems - the relaxed, obvious exposition, the lengthy scene etc, will limit the appeal that it has for a wide audience. Much of the early pages lack any conflict (hated by the middle-classes, but kinda good in a film).
The writing is good overall - but it comes across a little too much like a novel - quite over-written in places.
You've put in a couple of 'SAME TIME' bits on your mini slugs - they're not really needed as this is implied by the mini.
Okay - I'm on page 12 now, and we've got to the dizzying heights of 'laboured breathing' in the excitement stakes, so I'm going to pull out - I need a nice cup of tea, just to calm down.
Seriously, this may be adaptable to an evening drama, or maybe a radio-play - the dialogue is fairly realistic, and you've certainly caught the sensibilities of the Brit middle classes - but I don't think this is going to have wide-scale appeal outside Blighty.