I have a victorian back to back terrace with a small cellar (2m x 4m). Until about four weeks ago the cellar had been damp pretty much all the time but recently (clean) water has been coming in at the rate of about 8 - 10 buckets full a day. It hasn't been coming in every day but intermittently and not necessarily on the same days that it has rained. The water is slowly seeping in under the flagstones at the front of the cellar. The water board have dye tested the drains and they don't think it is mains water so it seems to be ground water coming in. Nearby neighbours have had similar problems from time to time. What would be the most effective fix? I was thinking of putting down some kind of waterproof membrane and I presume I would have to lift the flagstones and put it underneath? Even then I am concerned the water would find some other way in or would just get diverted to my next door neighbour. Any advice greatly appreciated.