Hi, We had a Woodburner installed last year (by expensive Hetas Engineer !) It was used between November and March and since then has been empty/dormant. Two days ago three of us were in the sitting room when we heard this 'thud' come from the stove area. We have checked that the cowling is still in place which it is, and that a bird could not have fallen down the chimney. We are wondering if the chimney liner could have slipped - are these attached to the cowling ? I believe they are. The noise could have come from next door, whose fireplace is in the same as ours, just the other side. Any ideas on how we can check this out? I don't want to call back the engineer until I am sure if it IS the liner which has dropped.