widget width on mobile device

Hi,
Brilliant plugin, thank you, it has been the mainstay of our site for a long time.
We are using Custom Community 2 theme.
We have placed the widget in the left sidebar at the top. The widget works fine on PC browsers and tablet browsers. When we look at the site on a mobile phone, the widgets in the sidebar stack up above the main part of the page but the Simple Calendar Widget is the full width of the screen and not just in the sidebar.
Not the most experienced web site builders as we are local people helping a charity, community centre but any help would be appreciated. Many of our users look at the events several times a day on a mobile device and now find it difficult as they have to pan across to see the event times.
http://www.myesm.co.uk
Thanks in advance.
Abdul