Located on the edge of Wimbledon Common, next to the Windmill Museum, is the Windmill Café & Tea Room. I visited the tea room for lunch one day with a friend who lives near by. She had pre-warned me that she hadn't had very good experiences there in the past, so I wasn't expecting much.
It isn't the nicest looking place - it is in need of a freshen up I think. The staff were not particularly friendly or helpful, though they were quite busy. You have to place your order at the counter and you will be given a number, which will be yelled out once your meal is ready. Take your pick of a table inside or out.
Food wise, you can order one of the big breakfasts, sandwiches, toasties, baguettes, other hot meals and there is also a selection of cakes and pastries.
I had a Ham & Cheese toasted sandwich (only lightly toasted so ham was cold and cheese not melted) and Jen had a Bacon & Avocado baguette. The food was ok, but nothing special. Oh well, I had been warned!