we had condensation/damp issues in our victorian terrace..
we bought one of these..
ran it on full in each of the rooms for about 6 hours or so and the difference is night and day now..!
got rid of the damp patches on walls and the whole house just feels drier now..
it sits in the attic room now and we run it on the auto 50 setting so it only kicks in when the humidity rises above 50% and we only keep it on during the day.. its pretty quiet when in the low mode (which it is most of the time) but i turn it off at night because ive got massively sensitive hearing..!
emptying it every couple of days at the moment and its usually about 2/3rds full in the 5 litre tank.. i think id find it a real pain if we had got one with a smaller 2 litre tank.. though they can be setup with a constant drain if you have a drain nearby..
ive found increasing ventilation helps massivley too.. open the window for 10 minutes after a bath / shower to get rid of the moist air.. open the window while cooking etc..
and if you have double glazing make sure the trickle vents are open (or you open the window to the slightly open notch but still locked) to help with ventilation in any moisture producing areas!