Wow, that's cool. 
How did the first SBS double deckers look like???
And other than Leyland, what other brands did SBS try out for
its double decker trial??? 
Guy Victories, Dennis, Daimler, Volvo, etc???
SBS tried a few models of DD in the 80s. They were:
Dennis Dominator - This bus was actually en-route to Hong Kong
but stopped over in Singapore for a brief demo period.
Volvo-Ailsa B55 - The only front-engined DD SBS ever
used
Volvo B10MD - The only mid-engined DD SBS ever used.
Scania BR112DH - SBS not a big fan of Scania DDs. This is the
great-grandfather of the K310UD.
Mercedes-Benz O305 - Started out with the Willowbrooke model,
then the Alexander demo. Eventually, 200 units were registered
between 1984-86.