Thank you everyone for all your advice. Much appreciated, this is just the sort of information I knew I could find here.

I have just booked a flight out to Hong Kong (thanks ant_west, I haven't been for years and the flight time is perfect) and a flight back from Tokyo. With an extra night and Avios hop in between it should be ok....amusingly my colleagues agree with trueblu and want to know why I am going to the other side of the world for a quiet drink and a lie in.

All the China information was great but actually made me realise that I should probably save it for a full holiday plus Tokyo hotels are so expensive that I am not sure that I could ever stump up for more than a couple of nights there.