Actually, I chose to go private for the scan (and skip the free public one) for that reason... I didn't want to wait for the result, though in hindsight regret that because it was not exactly cheap (1300hkd) and waiting for a couple of weeks wouldn't have been that bad. But I'm 31 and had already had a clear scan for my first child; think I would have waited had it been my first also though.

I think something to think about is whether in the case of an adverse result (which I still think is quite rare even given your age) you'd want to do a second OSCAR or the more advanced test which is amniocentisis. OSCAR only tells you probabilities but amnio gives a more confirmed results (there are some risks which is why they don't do it for everyone).