The sample data usually shows up when there's no real data for the time period. The first thing I'd check in this scenario, though, is the date config on the LEM. Under the APPLIANCE menu, enter DATECONFIG and then hit enter four (4) times. The LEM will return the current date, time and timezone. Are these correct? Are they drifting over the course of 24 hours to 15 days? By default the LEM syncs with the virtual machine host for the time. Is your host set to sync with a good NTP source? Your system info says GMT and your profile says the UK, but I would start there.
There's also a big drop in your "Events per Minute" chart. Have you run a Database Maintenance in the Reports console to see if events are still getting into the database? If you run a DISKUSAGE under the APPLIANCE menu, are there events being queued? Do you have a partition close to or at 100% full?