Ok got to the bottom of this but not straight forward. I bought another dongle just to try and it paired with the headset no probs. However...... I had to go download drivers from Broadcom rather than the windows default to get the headset fully working, independently of my PC speakers in Ventrilo. Oh and one other caveat, when the PC goes to sleep it loses connectivity and have to do a bit of jiggery pokery to get it working again. Shall have to see if i can get to the root cause of that!!
Remember: Amateurs...built the ark.
Professionals...built the Titanic
All spelling and grammatical errors are left in on purpose