High Tea Catering?
If you are willing to make the tea on you own, you could rent a Samovar, at a rental shop. It makes the best tea and serves many. From there you could buy your sandwiches etc. My church group honoured a member and we had a tea in her honour. I was responsible for the tea service. If you are considering doing it on your own, I can make some suggestions. You can purchase some lovely teas at Akhvan, they have great teas.