They certainly are left-aligned: they are famous (and notorious) for it. The "Guardian-reading lentil-munching sandal-wearing lefty" is a popular caricature, I've even seen people criticised during debates for being a "good Guardian-reader" (i.e. a part-time socialist).
But they do publish articles on relevant topics, and are prepared to stick their collective neck out for important stories like the Snowden case. They are probably a few notches above the open sewer which characterises much of the rest of the UK press, and it's clear that many people on HN find them relevant, if not always correct.