In terms of airports I have to be the deviant.

My home airport in the UK is MAN and it is much much preferable to LHR. I find LHR to be just a vortex where time just seems to disappear - heck I was forced to buy a one way to LHR last week and I am allowing 4.5 hours from airbridge to a train up north departing from EUS.

One time I was on TK from IST and even with a 3.5 hour I missed my train and had to rebuy my ticket .

KIX is also a much nicer airport than NRT and nearer to my base of operations in Japan.

I would agree its demand - there used to be a LHR -> KIX service via JAL but it got scrapped from T3. MAN is expanding with their direct HKG service and China services - having a Japan service would seem the next step for me ?.

The UK is not short of options to get to Japan
SK via CPH
LH via FRA / MUC
TK via IST
AY via HEL
KL via AMS
AF via CDG

And a few others like Swiss.

For some flights especially the AY ones there isnt that much differencce in time - as short as 14 hours vis 10 / 11 direct so the business case for a direct flight is hard but I still would like to see a direct competitor compete for traffic up north outside of LHR.