The Tea Palace shop in Covent Garden has a deceptively small storefront since they have a large basement area full of tea. The first floor is dedicated almost entirely to the counter at which you order teas by weight, whereas the pre-packaged tea is downstairs. Also downstairs, in front of each pre-packaged tea, is a sample of the tea for smelling. There were also 5 different teas brewed for free samples, which definitely sold me on at least one tea. The employees were very helpful and were very willing to help you find a tea you might like if you didn’t know what you were looking for.
At the counter for tea by weight, they had three different tin sizes that you could order. It seems like they must have also had a paper pouch available too, but I can’t really remember; I just remember when I asked about the minimum tea amount to purchase I was given the options of the tins. There was a 100g, a very large tin (unsure, possibly 250g?), and small, 30g sample tins. Which is really a more volume based system, but they fill the tin and then charge you a set price in the system, presumably based on the actual weight of the tea in the tin. This is actually the only shop I visited that sold sample sizes, which I appreciated a lot. The sample tins are very cute, too! I initially ordered 3 samples, but they were having a promotion (for the anniversary of the company, I believe) where if you spent £20, you got a sample tin for free. So I obviously then had to (by my logic) order two more samples, so I could get a third for free. The employee getting my tea was very helpful in suggesting other teas to sample, and she even rang it up so that the most expensive tea (a white peony with rose) would be the free one!
I definitely suggest visiting this tea shop if you are in London; they have a lot of very nice teas, are very helpful, and I definitely dig the 30g sample tins!