The Yogscast - My first thoughts were ISTJ for Lewis, ENTP for Simon. Then I moved to ENFP for Simon and considered I_TP for Lewis.
Hannah I think is an STJ, probably I.
ISF_ for Lalna? I__P for Sips?
my take on this:
Lewis : INFP - a lot awkwardness, sometimes looks douchebag-ish due to this, but have a shine in his eyes when he supports a cause.
Simon : ESFJ - the screaming upon seeing adorable objects. not really a structured ESFJ, but you can see how stable he is when he is on public.
Hannah : INFP - not much i can remember why on my mind right now, she's very different from lewis, but still shows INFP.
Sips : ISTP - just a hunch, reminds me of an ISTP friend of mine.
He definitely shows a lot of Te and Si based humour. I watched a few of his videos for this conclusion. They were also all hilarious. Of course I could just be typing a persona here...
Or maybe it is Ti+Se which would be more ISTP. You could say he shows tertiary Ni when he is coming up with the humourous possibilities for the picture on the wall of that first video or his potential actions with the lady.