The instructions for that fan indicate that it does have a humidistat, but it's not adjustsble. Which is unusual.
It does have a "two speed" mode, though, instead of "humidity tracking"; you could try that. See figure 3 of http://www.envirovent.com/product-downloads/filterless_extract_fan_230V_V9_LR.pdf
It does have a "two speed" mode, though, instead of "humidity tracking"; you could try that. See figure 3 of http://www.envirovent.com/product-downloads/filterless_extract_fan_230V_V9_LR.pdf