There is a limited set of results returned. Change the date filter and you should get more recent records.
I think I worked out what it is though... On the top of the page, there is a note stating "The maximum number of visible records is limited to 100.". However, the max number it is displaying for us is 50.
Would it be possible to get this limit raised to showing (say) the last month of usage, irrespective of how many records returned? 50 is quite a low limit.
Btw - while roaming in Northern Ireland, are incoming calls charged or are they free? I wasn't sure.