The Gresham lectures are one of many free institutions in London, usually covering politics or economics, either in the abstract sense as a lecture series on theories of a particular school or surveying the history of a region, or applied to topics of current debate.
Simon Thurley, known for his role as conservationist and head of English Heritage, recently spoke at Gresham College on the architecture of London. Now those lectures are available for free as a downloadable recording, and I think this one on restoration and imitation sounds like it’ll be especially interesting.
Personally I think the most sympathetic buildings can be those in a new vernacular which somehow speak to their surroundings, either imitating their proportions (but not their style), or enlarging a detail in the older building and making that the focus of the new, or updating the ideas to a modern equivalent. Whilst I hate the mix of blandness and aggression in many of the new office blocks of Canary Wharf or the riverside, I do like the Shard, and also the diversity of London. The city needs to keep moving.