hmm. graphing should be continuous because time and data are continuous over clock changes. What should be discontinuous is the labelling of the x [time] axis.
It was a bug drawing the graph.
The CSV download still goes 0059(BST/+0100) -> 0100(GMT/+0000).. this should happen 0159GMT though. If you look you will see 0159-->0100 though so it's a mis-classification of the time zone.
What I was saying was that you may find that after the end of today, if you view today's graph, it will finish at 23:00, as it's a fixed 24-hour graph, if I remember correctly. We're going to fix that when we redo this interface completely, hopefully in the next few weeks. The XML data is there, and the CSV will be fixed tomorrow anyway, so you won't lose any data.
seb