Catered afternoon tea?
Some of the pastry chefs (and/or their students) at Cambridge Culinary might pick it up on a lark.
ETA: what a great idea - if you find someone, I'd love a report! If they have a source for non-jar clotted cream, I'd double-love a report!
also-ETA: when talking with the caterer, you'll want to distinguish between "afternoon" tea and "high" tea, since the name can mislead a caterer who doesn't know. The Dowager Countess drinks tea, afternoon tea or low tea, while the servants drink high tea.