Please report it on the contact page, using the "report an error..." category
Yes, it's a Google Calendar. Search the public Google calendars for "LongdenParish", and display it on your own page. Or, alternatively, visit the Parish Diary Page and click on the google link at the bottom right.
Yes. We can display your calendar over the parish calendar. Naturally, your organisation must interact with the people of Longden. Email email@example.com with details.