Assuming that cost isn't the overriding factor, and if you're used to BA on non-stop flights it probably isn't, I think your use case is tailor made for QR. My preference on QR would be QR8, if the price is right, partly because this is the new Suites flight but mainly because it gets you onto the 4 p.m. arrival in HKG (rather than 8.30 p.m.) which puts you in the hotel mid to late afternoon UK time when you really need to be thinking about going to sleep!

MH's timings are even worse in that respect with a near-midnight arrival.

On timing alone, Finnair wins this by a mile, being comparable with a direct flight, but you have to take into account the viability of the connection (though if you are leaving on Sunday you should be able to be rebooked onto the Monday flight arriving at 8.10 a.m. on Tuesday as a worst case scenario). I've never flown AY long haul but others have complained about the quality of the seat for sleeping.

45 minutes should be absolutely fine for connecting in HEL unless there's a bus gate, at which point it's still doable if the plane is on time.

Of course you might find it difficult to go back to BA after these!