bathroom extractor fan

Hello I've never personally fitted this fan although a quick Google search showed prices over £100. A fan I have used with customers before in 'problem' cases is the ST100HT 'silent tornado'. Seems to have the same extract rate as your Vectaire fan but is quieter, uses less energy and from 'extractorfanworld' comes out at £88 with the delivery. A couple of important factors not mentioned in your question are the placement of the fan relative to the source of humidity (bath/shower), the ducting length and route, and finally the availability of fresh air to enter the room as you extract the humidity. It is no use having the fan trying to extract the air if there is no source of fresh to create a flow, the fan won't ever create a vacuum in the room.

Axial fans are much of a muchness. If your still having problems with humidity then you need to examine the issue further. Axial fans have little actual sucking power against negative pressure. That is they work well in ideal conditions when the air is free to move but hardly at all when air pressure is slightly negative to the outflow pressure. Upgrading the fan would make little difference. You need to ensure there is sufficient flow of air to the fan when it is operating. Also there will always be a little moisture left over so heating is essential in most bathrooms to drive out any excess . Also mold resistant paint and regular cleaning are essential especially if the property is let out. Good Luck.