Water through external walls?

My son has a house built about 1940's with no cavity walls as far as can be found is that the walls are breeze blocks or similar laid flat side down not edge wise and then rendered on the outside.
He has had a lot of water penetration since moving especially above the kitchen window, not a damp patch but actuall dripping in.
The roof has been checked and that is fine and he is now having new UPVC windows fitted and apparantly when the old window is removed it is obvious how wet the walls are.
Do you think a coat of weatherproof paint on the renedering might cure the problem and if so which one would you reccomend?
Thanks for any replies.

 

If it's dripping in weather proof paint isn't going to do some magic. Needs determining whether the problem is the roof or the render depending who declared the roof as not having an issue.

 

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