High Ground Levels

Hi
I live in a very old house with high ground levels at the front of the house. We do not have any indication of damp inside the property other than a sligh musty smell in the dining room. As a precaution I have had the edge of the patio removed and have dug down to below internal floor level. I have painted the external walls (below the oold ground level) with black bitumus paint to act as external tanking). I am now propossing to backfill the trench with 3/4 inch gravel back to the same level as the patio. Only problem is that the trench fills with water when it rains as we have very heavy clay soil. This water is sitting below internal floor levels and in most places is actually below or level with foundation levels. I can't afford to have a whole drainage system installed. Is backfilling with gravel and relying on the tanking I have done going to be alright or is there antything else I can do without going to huge expense?
Any help gratefully received.
Regards to all

You did not mention if you had gutters and downspouts installed . If not, that would be all you should have to do. You need to get the water away from the foundation. The gravel for drainage is a good idea, but it should go down to the tile around the footing, but it sounds like your home may be too old for tile. I hope this helps.

You did not mention if you had gutters and downspouts installed . If not, that would be all you should have to do. You need to get the water away from the foundation. The gravel for drainage is a good idea, but it should go down to the tile around the footing, but it sounds like your home may be too old for tile. I hope this helps.