Vectaire Fan Stuck on Full Speed

[Ripley5000]

I have a Vectaire SBAF 125/2 extractor fan in my apartment that extracts from both the bathroom and kitchen. The fan is the type that is designed to run continuously and has four speed settings. The problem is that the fan runs at full speed all the time and changing the selector speed on the controller does not work. My plan was to simply change the controller unit (as a whole new item is £450 and not needed as the fan and housing are ok) but I cannot find anywhere that sells the controller.
Does anyone have any suggestions of where I might get a replacement or suggest an alternative - note that the controller has four speeds and also a boost switch which allows the use to boost the fan when required.
Thanks

 

[JohnD]

When did it last work?

(If ever?)

 

[Ripley5000]

It's on a property I've just bought so I don't know when it last worked.