Having never had an issue with it before, the two single glazed windows in the north facing wall of our dining room now have terrible condensation on them constantly and it's pooling on the sills. The radiators have been temporarily removed for plastering and decorating and the carpet was taken up. In addition, a low level vent was blocked up as we were advised by the gas engineer that the balanced flue gas fire didn't require it.
The plaster has now dried. I've run a dehumidifier in the room and I've also stuck an oil filled radiator in there, though not together due to limited plug sockets. Neither has made any difference to the condensation.
We're going to have to reinstate the vent aren't we?