Ours is a 3 bed semi but with 4 floors. I was concerned that just the blower would be too cold so I bought the one with heater.
The fan on ours has speed settings 1-5. I started on 3 and it did reduce the landing temp and my sons bedroom temp by a degree or so which was very noticeable (it is a small landing) I then turned the fan down to 2 and you couldn't notice any difference or feel a draught.
I haven't used the heater once since getting it. However it is wired in using a cheap wireless room thermostat so that I could switch it on easily without going in the loft.
No mold anywhere in the house since we installed, and Windows very rarely get steamed up, in fact nothing like they used to
Thinking about it when I did put the heater on to see what it was like, it only made marginal difference, but last winter didn't get that cold in Yorkshire