Any wheel in/on the car has to be legal, even a spare, but it is not illegal not to have a spare, ie if you carry a spare wheel it must be legal, or leave it at home. Any Renault wheel/space saver will fit as long as the PCD is correct, fit this to the rear and you don't have to worry about clearing brake calipers. If the puncture is on the front fit the rear to the front and spare to the rear, simples. If you must carry a spare make sure it is secure, as in an impact, a loose wheel can reek havoc.