Welcome to the Forum Graeme......you won't be disappointed joining the Shopbot clan
I don't have the desktop and I'm sure the desktop owners will chime in.....but guess it will be similar to the other PRS systems. I got a 1/4" & 1/2" collet with the Buddy and I also ordered a 1/8" as well but I mostly use the 1/4" one. The collets are similar to what you have on a hand held router only much higher quality for the spindle.
I recommend you also get the starter kit.....I did and it was a well worth investment when starting out.
Cheers
Buddy 48 Standard with 2.2 Hp Spindle with standard and 6' stick. Aspire 10.5
2.2Hp universal 4 zone Vac Table