which scales are best?

[thirtysomething]

Hi,
I'm doing WW online and went the whole hog and bought some WW scales (at great expense) but they seem a bit too inaccurate....they fluctuate massively (up to 7lbs) so some days I'll have lost 3-4lbs then the next day (after sticking to WW points all day and doing an hour cardio workout!) I'll have put 7lbs on! My clothes are getting a bit looser so I must be losing some weight. It's not just me either as DP isn't on a diet but eats very healthily and he says they vary for him by up to 7lbs! I've even tried marking the position on the floor so they don't move about! Can anyone recommend some really decent scales?