I have been here several times, and always regard it as a safe bet in an area where 'nice chain restaurants' can become stretched to the limit during the tourist season.
Although you can't book there is a bar where you can wait and have cocktails or tea (which is a whole flower and slowly unfurls in the hot water).
I go in the day and have their set lunch menu. Even though it is a set menu, there is a good variety and the portions are ample. This is a really good place to take a veggie because of the variety of the menu.
The staff are very polite and helpful, even when it's busy. It is a great pre-theatre or post-tate modern place, ideal for a daytime date or a lunch with the girls, or even a family.

Ping Pong is stupendous! Seriously good food and our waitress was just so sweet and helpful - she ensured Ping Pong gets a 5 star review from us. I wish more waiting staff were as good as her.