Our neighbour recently laid a porcelain patio. The old patio was slabs on sand so water used to drain away. Obviously the new patio isn’t permeable and now surface water runs off the patio into our garden and it’s flooding. I’ve looked, there’s no drains installed and the patio fall is angled to drain into our garden. Surely this isn’t allowed as the slope isn’t natural it’s man made. I’ve raised it with them and they ignored me. Help!