I currently use Moyra stamping polishes. They have UK distributor and really good price. And I like them much more than Mundo de Unas or Konad. Unlike MDU they don't have strong scent and they don't separate, so no need for shaking or stirring. Also, I found that MDU does not pick up very well on clear jelly stamper heads, so that's another downfall. Much better opacity than Konad.
I just find that Moyra is so easy to stamp with, that even 3yo could do it. There are some YouTube tutorials - take a look!