I had a look at the various reviews before purchasing my ticket, deciding that at worse I will be able to sleep and put up with indifferent service and average food.

In reality, I found the following.
The seat on the 777 and A350 is a single seat (a suite with a door on the A350) which does everything you want it to. I would prefer to have had a cloth covering instead of what appears to be a cheap leather, which doesn't breathe at all. So I was fairly warm a lot of the time. If you end up on a A330, you'll have the 2+2+2 config which means climbing over the legs of your neighbour to get to the aisle. But in my case the cabin only had 7 pax in it so not a problem. And the A330 seat is cloth covered and no footwell, so in all probably a better sleep.
One criticism though is that they made enough noise with announcements to wake you far earlier than necessary, like around 90 mins from landing! BA normally does this at 40 mins from arrival. That was annoying.
Food was better coming home than heading out. That said, all of what I ate was pleasant enough, the seafood was actually quite delicious. I mixed western and eastern choices. Very limited wine list (red or white...) and snacks available during the flight. The crew are keen to get meals served very fast and you'll be eating within an hour of take-off.
Entertainment is pretty basic. Unless you like Chinese films, bring a laptop full of stuff to watch. You can plug it into a mains plug at your seat.
Service was actually very efficient, pleasant and orderly. There is a language issue at times for English-only speakers but I thought the crew did a very good job.
Lounges - LHR was the worst as it's quite small with little food offerings. PVG has two lounges, depending on which gates you leave from. If it's the G gates, then the new lounge there is spacious, some nice local food, showers, nap rooms, etc. All fine. I had a nap in the nap room on the 7 hour wait heading home from MEL.
Summary - I got what I paid for, I went in with lower expectations and was pleasantly surprised. MU are not QR by any stretch, but at nearly £2K less, who cares? Would I use them again? Yes, unless the price between MU and a OW carrier was small, as I have had to forgo my status on BA being renewed with the lost tier points. That said, I credited all my flights to VS which will come in handy on VS or DL in the future.