What Venezuela did was closer to communism than socialism. And they didn't just drive foreign investment out and nationalized, they essentially stole and took over most foreign facilities the businesses had in the country. And then took a super-hostile stance towards the US which didn't help their economy either. That's on top of lots of corruption and fairly dictatorial laws. The UK is socialist, and is nothing like Venezuela.
I assume this is kind of a backhanded swipe at Sanders, since so many opponents to him really jumped on the socialist part of him saying he was a democratic socialist (they always leave out the first part of that). It was a poor choice of words by him since he's more of a reformist in some areas that need reform, and made him an easy target by leaving the democratic part out and then painting him as a radical like Castro or Hugo Chavez which he is clearly not.