I had a little dosa snack at Vasanta Bhavan after having a proper dinner at Thattukada (which is having a massive duck roast for Christmas, by the way.) Their rava dosa was probably the best I've had in London. Super crispy! It also comes with three chutneys and sambar all for an extremely reasonable price. I definitely need to try some more at this place. It's menu is massive for a vegetarian spot, by the way.