Advanced Custom Fields repeter field expiration

Possibly better than strtotime, as you already know the date format would be date_create_from_format(). Something like:

$course_start = date_create_from_format('dmY',$row['start_date']);
if ($course_start > date('dmY')){
        echo '<tr>';
        echo '<td>' . $i . '</td>';
        echo '<td>' . $row['start_date'] ;

        // Check, if "end_date" field is not empty
        if( $row['end_date']) {
            echo ' - ' . $row['end_date'] . '</td>';
        } else {
            echo '</td>';
        }

        echo '<td>10am – 5pm</td>';
        echo '<td>£' . $row['course_price'] .'</td>';
        echo '<td><a href="#" class="button orange">Book Now</a></td>';
        echo '</tr>';
        $i++;
    }