Water seeping up through cellar floor at the same point

Lois71

Hi I noticed a damp patch on my carpet in my cellar (which was tanked 10 years ago - although i now know there is no pump). It has been fine for 10 years. The water is coming up at the same point (middle of the party wall where the wall meets the floor).  I have been round my neighbours and his is fine, I have checked the main water pipe behind the dry wall which seems ok and feels dry.  I have run a dehumidifier for two weeks then left it, it took a week to start seeping again. I then run it for over a month, turned it off and it started again within 30 hours. Who can I contact to deal with this??? Has anyone had similar and can recommend anyone to find where this is coming from? TIA