Just to let you guys know we have a Willerby New Horizon. We have only owned it a couple of momths. However, every time we go to the van we have around 40 dead flies around the patio door area and the same in the bedroom. These are the only two rooms which have velux windows. When we opened the velux window there were dozens of flies inside the sill of the window. We have bought new Filters which we fitted this weekend and we also used a clear sealant round the edge of the Velux window where we think they may be geting in. We took off the ceiling air vents which do not have mesh on them so we do not know if this is another place of entry for the flies. I can hear them buzzing in the roof space but my husband is reluctant to kill them with smoke as he said that it would mean we would have lots of dead flies rotting in the roof space. I know they do fly away in the spring but its really upsetting to have the buggars. At night when I am asleet I can hear them and in the morning guaranteed there are a few flying round the bedroom. They do die very quick so i guess i should be grateful. Finger crossed this weekend we do not have any after the work my husband has done. Will keep you all informed.