Problem for him is, that he has not sworn the oath in the House of Commons. He will not be back in London until after the Queen's Speech, which is the deadline when all MPs have to have affirmed or taken the oath.
Unless the Speaker lets him off, if he sets foot on the floor of the House when he gets back, he will be fined £500, and his Bethnal Green and Bow seat would be automatically vacated.
Though didn't Gerry Adams also refuse to take the oath, and manage to retain his seat (not to mention his Westminster office and parliamentary perks), merely forfeiting the right to enter Parliament? In any case, it looks like the voters of Bethnal Green won't get much in the way of democratic representation.