If it is only one child, fit a centre lap belt (or one front and back) as you can then take it out afterwards without and visual remains. Or am I being daft?
Paul,
If either a lap or lap sash belt is filtted you must still fit an aproved child restraint that is worn over both shoulders so that the the seat belt effectively becomes a four point safety restraint. With the lap belt this is simple enough as there are loops that the existing lap belt fits into. With the lap sash belt a buckle is fitted along the belt, effectively converting the lap sash into a lap belt, then the additional upper child restraint belt is fitted the same way.
Keith