We clean ours ourselves!!
Cover the room with dust sheets before you start, and find some strong string/rope. We use either a scrunched up olive net, or a baby cypress tree (sorry!!). Tie the string to both ends & one person stays at the bottom, and another gets up on the roof............take turns to pull it up & down a few times - cleaned chimney!!
There are things in the shops, that you can 'throw' on the fire - which supposedly clean the chimney as they burn, but I personally don't believe that they are as efficient as 'our way'!