After extensive internet research, I found the closest thing to a pumpkin patch within a 30-45 minute drive of Southwest London. Yesterday afternoon we went to Crockford Bridge Farm near Weybridge in Surrey. (http://www.crockfordbridgefarm.co.uk/).
Not surprisingly, I heard several American accents at Crockford. I obviously wasn't the only American looking for a piece of home. I couldn't even find a pumpkin in central London 11 years ago and now there's a pumpkin patch not too far away. Amazing. Crockford even had a few shelves in their farm shop dedicated to American groceries.
Walker enjoyed running around crazily, Moozles enjoyed the playground. I got to find the 'right' pumpkin. To my husband's annoyance, I can never just buy something. I have to make sure it is the 'best one'. I think this may be an American thing as my British girlfriends seem a lot more relaxed about their purchases. Can anyone confirm or deny?