Just secure a £40 bike bag from CRC/P-X/wiggle/merlin to the roof rails? Or just use a rack as normal (might cost you more on a ferry though).
The car does not have a tow bar and getting one fitted is too expensive
DIY fit one? My focus involved:
6 fittings holding the bumper on (screws and small bolts)
Remove the old reinforcing bar (4 bolts)
Cutting a credit card sized piece out of the black plastic underneath with a bread knife
Install the towbar 10 bolts, 4 to the car, 4 assembling the towbar and 2 holding the flanged ball onto the bar.
Torque wrench helped, but they were all ‘swing your whole weight off the scoket wrench tight’ and no grease on the threads.
Re-fit the bumper
Electrics were more involved, but still only too another couple of hours.
Cost £80 for towabar and relay electrics (don’t splice them directly into the wiring, it could damage the ECU) and £60 for a s/h aiston bike rack.