Doing works to my own place and we have a similar middle of plan bathroom with no external walls/windows. Your duct run is similar to ours (length wise) and from my in-depth conversations with Vent-Axia and Nu-Aire is considered pretty long.
We ended up going for a Vent Axia ACM100 extractor fan which we paired with a speed transformer to boost when the light is turned on and a overrun timer to let the extractor fan run for a certain amount of time post light switch being turned off.
It is an absolute minefield so feel free to message if you need anymore information
Doing works to my own place and we have a similar middle of plan bathroom with no external walls/windows. Your duct run is similar to ours (length wise) and from my in-depth conversations with Vent-Axia and Nu-Aire is considered pretty long.
We ended up going for a Vent Axia ACM100 extractor fan which we paired with a speed transformer to boost when the light is turned on and a overrun timer to let the extractor fan run for a certain amount of time post light switch being turned off.
It is an absolute minefield so feel free to message if you need anymore information