Ok - here are the answers to the How Old Am I? buildings quiz.
Holborn Station - 1906
St. Anselms & St. Caecilias Church - 1909
Aviation House - 1957
Victoria House - 1932
Tudor House - 1690
Apparently I came second in the competition (27 entries on the day of the walk), just being pipped at the post on the very last question. Oh well!