I would wait a turn and build an IC in a useful place. If you build it in J1, then it will mostly be used against China and perhaps Russia. HK and Singapore are way better options. From Malaya you can be in India in one turn (with fleet), in Australia, all of DEI and back to Japan quite fast. Land units are also quite close to Burma road (Chinese lifeline).
So if you decide to attack the UK on J2 then I would build an IC on J3 in Malaya or Kwantung. If you are going to wait longer then China (and perhaps Russia) may become too much of a pain and you need to transport units to the mainland.
My next game as Japan I will attack UK on J2 in Malaya. It gives you +3, UK -3 and ANZAC NO lost. And it is arguably the best place for an IC. For the attack I need a lot of transports, because I also want to take most of the other prices, like the DEI island, Phillipines and/or Kwantung. This gives your economy a major boost and the UK loses a lot of IPC income. I would also prefer to take DEI island from the UK instead of the Dutch controlled islands. You can take those later and the UK islands work both ways (more for you, less for them).