You're doing the right thing to make registration a priority Terenchion This would avoid a rant from a GP (or more likely the receptionist) if your wife tried to get treatment but was unregistered. Emergency treatment may be possible at A + E (Accident and Emergency) department of the nearest hospital.
You should also consider registration with a dentist for the same reason, but be prepared to go privately. There's not that many NHS dentists available, and a private insurance scheme could be worthwhile.