Ibis at Avenue Jean-Jaures is one I have used quite a few times. It's in a straight line from Gare du Nord and has an underground car park where bikes can be left. Nice cheap breakfasts too - as much as one can scoff 'n pocket for the day ahead (although one has to frown on such behaviour...) also, immediately opposite The Station is Aux Villes du Nord. Big fry ups available from Patricia and her staff there...space to the right of the café to lash bikes up. How are you dealing with the 'no bike bags on the Eurostar' business? Would take the fun out of it for me...paying extra for wheels.