I agree that €100 for a dinner at a 2* or 3* restaurant is considered inexpensive. Although lunch at many of these places can be quite affordable at around €60-€70, including Le V at FS George V Hotel and Les Ambassadeurs at Hotel du Crillon.

Anyway, back to London, I think La Tante Claire has closed.

For non-French food in London, I'd try The Grill Room at The Savoy.