apaddyinuk, not quite, "same airline" was intended to relate to using the same airline(BA) for both long legs, not that BA=VS.
Globaliser, thanks for regulation reference. I did ask VS if this would qualify as "open jaw" and they said "yes, but only if both legs could be flown by VS, even though they were separate countries". Their costing was on the basis that there would be two separate single tickets, which is where the extra cost comes from. I has naively expecting that, because they could sell return tickets to SIN through VS, that they would also be able to do this for the journey I was making.
Thanks also for warning on Emirates. I was not aware of the width configuration. Sounds the same as the "sub-contracted" BA 777 flights to Tampa and some Caribbean destinations that was much derided a few years ago. My only reference was Airline-Network, which suggests that Emirates have pitch of 34", whereas BA is 31", and Cathay and Singapore are 32".
Am also looking at HKG-SIN on another thread. I cannot find UA at less than £100, for the dates I am planning. Tiger Airways looks cheapest, but that is from Macau. Main problem is many schedules currently stop at end-Match.
NW