I flew BA J HKG-LHR-HKG recently and I have some mixed feelings about your comments:

Seats - Disagree - I think the BA J seats are comfortable for sitting and sleeping, though I had upper deck window seats both ways so perhaps this made a difference. I don't think I'd like an aisle seat as there is not much privacy and generally for J you'd expect some more privacy.

AVOD - Partially agree - The selection was acceptable, but not as good as CX, but I didn't like the touchscreen thing which didn't work reliably on either sector.

Cabin staff - Mostly agree - CX cabin staff definitely better though I don't think I'd call the BA cabin staff grumpy

Food - Disagree - I enjoyed food both ways, generally better than CX J. Maybe your catering services were screwed up due to the ash problem.

Coffee - Agree - I didn't have any coffee, but I did get served a lukewarm "hot" chocolate.

Storage space - Partially agree - Aisle seats don't have good storage space. Upper deck window seats have TONS of storage space in little bins (many per pax) on the window side. The drawer, which I presume is for shoes, is not very user-friendly.

In general, BA J is not a bad product, though it does feel kind of old. Combined with the excellent Arrivals Lounges at Heathrow, definitely a good experience and I'd certainly choose BA J over CX J if I was travelling with my wife due to the seat layout. If I was travelling alone, I'd probably go with CX.

BA J lounge is better than CX J lounge in both HKG and LHR, also (yes I know, it's debatable). But as a OW Sapphire I can use either anyway, at least in HKG.