Thank you! I've made a copy of the spreadsheet, massively tidied it up using your formula from the other thread, and removed the automatically importing weather data.

Here's the sheet with all the graphs: https://docs.google.com/spreadsheet/ccc?key=0AmkhuHmI5mk1dG5UYmRQQkUtOFVsNTBUNTJlalBRUFE&rm=full#gid=8

So, you can see the problem now: 2 of the graphs are showing all the dates, correctly, as expected. The other is only showing a few dates, with the time of 00:00:00.

I've re-imported all the data, re-made all the graphs.

In ALL cases, the date and time is dd/mm/yyyy hh:mm:ss

The other thing that is annoying the hell out of me is the way it formats numbers with a comma.
If I format the numbers as text, it looks fine, but then won't let me make a chart.

And yet, on one of the sheets, it seems that numbers are comma-free, but still behave like numbers.
Me confused!