I've never asked but had it proactively offered a couple of times; so not impossible and no harm in asking, but certainly not an entitlement. I don't know whether it's more likely with status or not.

So I'd ask but assume the answer will be no. If you aren't happy to plan to have 15hrs in London & treat anything else as a bonus then personally I'd look at cancelling the avios ticket and booking a cash one directly for the flight I want.