Thanks for the reply Dan.
No, I havn't tried a reset, I was hoping that I could achieve what I wanted to do without one. I'll give it a whirl later. Shame the logs aren't plain text files that would make it easy to manipulate the data, like a reset now and then paste in the data for 1/11 to 2/11 from the end of the previous file.
BTW, do you know what exactly the 'Keep weather station in hi-speed communication mode' option in the Options does? Does it increase battey consumption in the base station?