Damp patches, above skirting board in and around area of blocked up chimney breast

Hello elephant1_23, I would suggest first of all checking the condition of your chimney pots,and look for any defaults in the capping. Depending on ventilation and air conditions, condensation could be the cause. For under 5 pounds you can buy a home humidity monitor and find that one out. Once any issues on chimney(if any)have been resolved I would hire a dehumidifier and run it, if possible,through the night for a few days or until you see a noticeable change. Once dry keep a close eye on it over the next few days,if it was residual left over from rain water then it won't return.If you have resolved the condensation issue, and it still returns then i would recommend further thorough investigation. Hope this helps, Regards, David - Sirius Property