I will answer your question we flew to Vancouver and back recently with BA.
We flew economy, I wore a really lightweight merino matching top and trousers, no buttons zips etc, super comfortable and light, it was perfect, being comfortable makes a huge difference.
The seats were not too bad, they do recline and most of the BA planes have mouldable headrests, these made a big difference.
The TV was brilliant, a great selection of films, documentaries etc.
We were provided with earphones and a blanket.
We both thought the food was good, each meal is served with wine, we tend not to drink on a plane there were alternatives, tomato juice, water etc, tea and coffee was served regularly.
I took an eye mask and earplugs a cashmere pashmina which was much nicer than BA’s blanket and anti bacterial handwash with loads of tissues to wipe down trays.
If you look carefully at the layout of the plane before booking your seats you will see the areas with the drop down cots, guises is obviously where young children and families are and probably best avoided!
We didn’t pay to pre book seats we just did it as soon as check in opened online and got good seats FOC.
Our outward flight was fantastic the return not so good as we were delayed due to stupid people not going to the gate but wandering around the airport!
The flight was full of people coughing and spluttering and we got sat in front of someone with a child who constantly kicked my seat, the parents did nothing to interact with the child, not a story nothing!
On the whole BA performed well, we discussed whether or not we should have paid for economy + or premium and felt that it was probably not necessary for a 9 hour flight.
I hope this helps.