Fan set on 2 sounds like bearings have had it. Where do you get at the blower to replace it,  engine bay or inside the passenger compartment?

Inside, in the dash. I bet it is a right pain to get to!

 

It's not necessarily the bearings though, and it could be that debris has got in from the outside vent and caught in the fan. Is the pollen filter properly in place and in good nick? It may be possible to vacuum the various tubes with the filter removed. I've done that in another car, but not on a Citigo/Up!