This video shows the differences in the types of tea you can get in London at different price points. What option out of the three would you like? Personally I would go for the 80p option, but that is just what I am familiar with!
#6 I'll try to explain it, it's difficult not just because english is my second language but also because I don't discuss tea with so many people on that level so some flavours, mouthfeel etc I don't even have in swedish.
First of all there is a difference between pu-erh and black tea (and even though they don't say it I'm willing to bet that it is pu-erh in the last tea place in the video, aging tea is rare. I's almost only pu-erh that is aged with some exeptions.)
Too young pu-erh have a sharper, often more bitter taste than matured pu-erh. Mature pu-erh have a rounder taste with more umami, it maybe don't taste as much as for example black tea the first brew but aged pu-erh can be brewed many times (my record is 14 times on a 6 year old black pu-erh). If they had made many brews on the "posh tea" they would have noticed a big difference.
Older pu-erh also have more tones that come through while in a younger pu-erh these are overpowered by the sharpness and bitterness I mentioned erlier.
I think that is the best way I can explain it, now atleast. If you want to learn more I recommend that you Buy a green pu-erh, try some and take notes ant then store the rest until next year and compare your notes from last time a year later.