It's been a while since I added to this.

But for those of you with android devices the following app might be a godsend.

Y5 Battery Saver
This wee application turns your wifi on and off depending on your location.
So for example when you arrive home it turns the wifi on, but once you leave heading for work it will turn it off.
Then for example if at work you had previously connected to a wifi it will re-enable it for you.