They aren't speaking English, they're speaking Chav British.
hmm cant say i heard much chav british in that video, the presenter has a strong accent for sure though.
also
I love this show. not the most unrealistic in terms of fighting and what they wear (hell i watched Hammer of the gods and the vikings had no shield, one had a clay-more one had two swords etc
) even if it is totally histrionically accurate.