the London Harness Horse Parade in Battersea Park is really good - we've been in previous years, and we're going again on Monday. It's free, and the horses look so fabulous, all groomed for the occasion, and the drivers are friendly if you want to chat. Here's a link about it:
news.bbc.co.uk/1/hi/special_report/1998/04/98/easter/75989.stm