The Sanders quote was a misattribution, that has been recited so many times that looks properly sourced. Quillette has a properly researched defense of Sanders:

https://quillette.com/2018/03/10/sanders-venezuela-meme/

Corbyn, on the other hand, has explicitly and often praised Venezuela and Chavez. There are plenty of primary sources, e.g.,

https://twitter.com/jeremycorbyn/status/309065744954580992?l...