1/ Given that the HEL flights land at T3, you're/we're SOL Even if at T5 you'll get to queue at UK Border to go landside and it'll probably get nightmarish come next April... So thanks, but no thanks. LHR is high on my "avoid if you can for transit" list, together with FRA and CDG.

3/ I have no (serious) issues with the A359 seat, even being a gentleman of size Whereas the Dorm World just freaks me out. 2-4-2 is premium class - seriously? Facing backward, facing a complete stranger for xx hours, jumping over/being jumped over, the whole plexi divider thing - and this is just the hard product... In 2018 it doesn't cut the cheese. Yes, beats the back of the plane, but why go out of my way to use it when there are so many better options?

The one thing for Avios is that it is a more versatile currency, but often it's just cheaper to buy a revenue ticket than award + "fees"

If you're LON based, have Avios earnig CCs, etc - that's another calculation for sure.