Dig a deep trench around the property,adjacent to the affected walls, go just a bit deeper Than the foundations pour in some 10mm shingle, lay a perforated pipe on to with one end connected to a 100mm pipe that leads to a deep soak away. Put textile on top of the perf’ pipe to keep it clean and working, tank the walls outside with two coats of bitumen with a mesh membrane between the coats. More shingle, 20mm now. Backfill taking utmost care not to tear the bitumen. Brush all the exposed brick inside the cellar, apply two or possibly three coats of proprietary tanking slurry. Fix a membrane as per manufacturers instructions. If necessary construct a drainage gully around the perimeter and fit a sump pump to continuously remove any ingress. Then, after proofing the floor, build a studwork wall that has no contact with the outer walls of the basement.