After a couple QR trips now, I found that UK travel portal doesn't even show the possible options compared to travel aggregators which are also often cheaper. Calling in concierge doesn't help much as they see exactly the same rate and options you see on the online site. Thus, it is often easier to book directly or via aggregator with a longer connection time if you transit, as QR as it is actually a nice airport.

In summary, I personally haven't found any use for UK IAP, unless you are trying to accrue MR points