Thanks so much for your detailed reply! Sorry to bother but I have a few more questions: I believed that the cancellation deadline is 48hrs before pick-up time to not get charged, could you clarify on this? Because according to your advice it seems that you could cancel a booking on the spot, and keep another booking.

How common are 4WDs in the standard SUV pile? Could you give a rough percentage?

Around how much would the upgrade from midsize car to, say, a full-size SUV cost? Because if its cheap, it might be better to just upgrade at the counter. (the standard SUV booked online is not cheap). This also saves the hassle of making 2 bookings online.

What about the upgrade cost from standard SUV to full-size, if there aren't any standards with large boots? We have 5 large luggages to carry.

Thank you once again for your help!