I started a similar thread on April 22nd 2008, so it's definitely at this time of year that things start to turn:
http://www.enz.org/forum/showthread.php?t=17605
Although I must confess in our new house we haven't needed to yet, has anyone else needed to?
I also notice in the old thread Dharder replied 'what heating?'....I think that has changed now.