fruitcage

I have some flights on my screen at what I consider an attractive price and there is a button to hold for 72 hours for £5. If I add a car rental, there is no longer a 'hold' button that I can see, and I understand that an online BA Holidays booking does not benefit from free cancellation within 24 hours.

So the question is - if I use the 72 hour hold facility, will I be able to add a car and turn it into a BA holidays booking when I come back to the held booking to complete it? My risk would then presumably only be that the car rental price has increased in the interim.