Originally Posted by McG

I did this in November - JAL outbound from UK on the 777-300 and BA back on the 787-800. The only complaint about the JAL flight was the high cabin temp combined with wearing an FFP2 face mask for the duration of the flight made it uncomfortable.
The BA flight on the way back took nearly 15hrs and was by far the worst long haul flight I've taken. Found it really hard to get any sort of sleep.

I'm looking for GLA-TYO in September to go to the F1 race and am looking at nearly £1200 being the cheapest. Emirates via Dubai doesn't seem as bad now with the extended BA and JAL flight times.