Damp patches on concrete subfloor

[elleberry]

We are in the process of renovating an ex council house that has had an extension added about 20 years ago. It looks like a DIY job. In the "new" porch area of the hallway there are various areas of damp rising through the concrete which seem to move around. We have already filled one area at the base of the stairs with a specialist waterproofing cement for wet areas. But this seems to have possibly displaced the problem. At one point whilst digging up the floor in this spot my partner said the water was almost gushing in the hole and the concrete was very wet. This bit is now dry. Could the water table have changed causing a problem? The house is on a slight slope with the back higher than the front where the porch is. There is a patio and concrete slab at the back of the house with inadequate drainage which doesn't help either! The DPM on the outside porch wall also appears to fall short of the floor (I know why?) There may also be blocked guttering here exacerbating the problem. Basically what can we do that will solve the problem without digging the whole floor up? We can't afford to spend much money as we have none!! We moved here as we needed an extra bedroom for new baby and converted the en suite into a bedroom and still have lots of other big jobs still to finish basically it is never ending and doing one thing uncovers another. Please any advice would be much appreciated. Thank you!
I have a pic in my album of the problem but not sure how I attach it here.