BTW...
I have lived in poorly maintained private rented accommodation, and have battled in vain against icy blasts and know well the futility of ramping-up the heating-fuel costs without feeling the merest benefit, but I did not do so for long.
I hit upon the notion of using durable double-sided sticky tape (cutting the 3cm wide reels into three) and sticking it around the draughty window frame, and then cutting-up a polythene dust sheet to just over the dimensions of the window, I then stuck the plastic sheeting up as secondary glazing...and then sat back in my virtually draught-free, economically heated flat and watched as it was now the wind's turn to blow in vain in its attempts at entry.
N.B.
There is a clear danger in stopping all air circulation, especially if you use some sort of naked flame heater. But if there are draughty windows in rooms you use less frequently or in the hallway or on the stairs...every little helps.
P.S.
For those aesthetically-sensitive, and who may wish to fork our £20+ per 'large' window try the steel strip & tape combo (£0.89/foot)...
http://www.diy-secondary-glazing.co.uk/secondary-glazing-accessories-magnetic-tape-c-204_695.html