Ford Galaxy towball & electrics

In the process of buying a 2010 Ford Galaxy Zetec Powershift. I need a flange tow ball for the Witter cycle carrier and bumper guard. Will this interfere with reversing sensors in which case should I go for a removable flange type? Should I go for bypass or canbus? Fixed with by-pass is £285. Add £300 for canbus and further £200 for witter removable so £785 for deluxe. I don't want to waste money but also want to be safe. All advice gratefully received.