we are two adults and toddler in 2 bed flat with single glazed aluminium windows, internal bathroom and no extractor fan. condensation a nightmare but is worst overnight in bedrooms! there are companies who do secondary glazing for a few hundred pounds, also a company that you can attach a pvc panel to the window frame via magnetic strips unfortunately this isn't compatible with most sash windows. last winter we used this http://www.wickes.co.uk/Wickes-Seasonal-Secondary-Glazing-Film-6m2/p/210014 window film. it was so effective but unforch we didn't feel we were unable to ventilate the rooms we'd sealed off enough via the windows we hadn't sealed. this year we have a karcher window vac, the old model about ?50. it's really helping but does get a bit annoying having to do it a lot. several of my neighbours use dehumidifiers which they find effective but keep running 24/7. Also condensation much better when heating kept on as air will hold more moisture..