old house dampness and humidity

I have an old house with thick mud walls, the house was dry lined with inner battons and kingspan insulation with foil backing fitted between battons, however in the bedroom there still is alot of humidity even though no obvious signs of dampness any where, just a general feeling of humidity. The ceiling is wood but i havn't gotten around to putting insulation in yet, however i don't think this would make much difference to humidity. I don't know whether there is a damp proof course in the concrete floor, would it be a good idea to paint it with water proof sealant and then put down carpet? I have heard of people digging a trench around outer wall and then putting in drainage pipe and stone, would this do anything? The house is lower than some of the ground near it but this starts about 8 metres from house, has anyone much experience with old houses

Is there a rad in the room and proper ventilation?

Maybe it does not get enough ventilation ie. air circulation. This can give it a damp feel and leads to condensation or fungal growths that smell. Also does it get much heat.More often than not dampness comes from the inside of a building as you mentioned (Humidity)when the moisture in the air hits a cold surface.

Have you tried running a de-humidifier in the house? I know someone who owns a 110 yr old cottage, and has a de-humidifier on through the winter (and our not-so-warm summers!). I'm told they cost about as much as a fridge/freezer to operate.

yes i have got a dehumidifier this week, and it has definitely made a difference, there is a radiator but it is only on for a few hours in the evening when Im home, i think more heating and ventilation and dehumidifier should go a long way, the house is also in a farmyard which i think adds to the problem as maybe sheds in the farmyard maybe contributing to problem, this is another complicating factor which you don't have with stand alone houses. I think I will have to ensure that all run off water from sheds is going directly to drains and not seaping under ground