Can't believe that Tibits in Heddon Place is again not included on your list of best vegetarian places to eat in London.
But maybe it is intentionally Londoner's best kept vegetarian/vegan secret - indeed it is often pretty busy despite being tucked away, just off Regent Street.
In good weather the large outdoor seating is a joy as the area is pedestrianised so no traffic fumes .... sunny in late morning/early afternoon (earlier/later in high summer).
Your 2012 review described the food as unappetising which isn't the experience of ours or friends or numerous people (including fishing/shooting types) we have taken there. Indeed it has won awards.
So though you should re-review it, perhaps keeping it a best-kept-secret is best.