I second this great idea.

I bought some Horniman brand tea in the gift shop at the museum. I did not know that it was made and sold in the UK anymore.

The good old Horniman Museum has missed a trick, though. They do not sell it in their little tea/coffee shop/restaurant thingy. The young lady who served me tea also thought it a bit of a missed opportunity. She added though that the food part that I was sitting in was run by a third party.