If you have a Mac computer, you probably have iCal, the calendar software. There are other pieces of software (like Microsoft Outlook) which also use the same standard (see below) for displaying calendar data. In either case, you can subscribe to a live update of calendar dates. In this case, your calendar can be automatically updated with new aikido course events from this pages.
Alternatively, if you just want to try it out, and import things once, go to http://technorati.com/events/, paste the URL (web address) of the Courses page (http://www.cambridgeaikidojo.co.uk/courses.htm) into the box, select "Get hCalendar events once", and click on the "Do it!" button. That will generate a file which you can open with iCal (or another piece of software).
According to Wikipedia, this should also work with things like Facebook, Google Calendar, Windows Calendar, and so on... Experiment!