Jonas is only really just breaking through in the UK with "Robin Hood". He had another part in the Channel 4 series "Teachers" about three years ago, playing a schoolboy who was dating one of the (female) teachers.
I believe that he was born in Ireland but was brought up in Manchester. Certainly he has a Mancunian accent, which he used for his character in "Teachers" and which, strangely, he's still using for "Robin Hood" - there seems to be a general acceptance in TV-land that any northern accent can be used for a character from anywhere in the north of England, despite the fact that Nottinghamshire, Yorkshire, Lancashire and many of the other adjoining counties have very distinct accents!