Chris Plastow
A problem like this is solvable but great care is to be taken as to observe the exact area of the leak. It would appear from your description that the water entry is from above the waterproof tanking but still below ground. Usually this happens at the joint of the ceiling to the wall, there is a hole in this region. Resin injection may solve it or continuing the tanking sufficiently to cover the hole. This is only to be rectified by experts. Get quotes from rated people, set it at below £500
