Eurostar? Redeem Avios via avios.com, it's fantastic value. Departures hourly on the hour, only need to be at St Pancras half an hour before, easy to take tube, bus, rail or a cab from the Emirates. Heck, you could walk it in 40 mins at a pinch. You say you are overnighting in Paris anyway so stay near Gare du Nord for an easy run on the RER to CDG in the morning, or make the move on arrival and find an airport hotel.