Hello Paul!
At the moment there is no sound set for single download instruments. Basically it is no problem to use any of our collections with Sibelius. For all collections, where there is no sound set yet, please be aware that you have to switch articulations with MIDI commands from Sibelius. Here is how to do that:
Activate and open an instance of VE for the instruments in your score without a sound set. As sound set choose none.
For every instrument create a matrix of the patches you need with H-Span set to Keyswitches. To switch between patches, write the following Technique Text in Sibelius.
~Nxx,64 followed shortly by ~Oxx,64
These are MIDI commands for Note on and Note off. xx stands for the MIDI number of the Keyswitch. (24=C1, 25=C#1, ...)
Best wishes,
Andi