Ive searched the wiki and Googled everywhere, but cannot find how to use the 'PVR Hold Off (Hours)' in the Web manager (advanced).
Can I give it a series of comma separated, or a range of hours - e.g '9,10,15,16,17' or '9-17' so that the PVR doesnt run between these times ?

Are you talking about the option that's in Search > Recordings?

If so, when you mouse over the particular option is gives you more detail. I don't use the Webpvr but just from what it says in the tooltip then it looks like it accepts a number as an input and delays the triggering of the PVR by that number of hours.

Technically, it doesn't delay triggering, but rather prevents a pvr run from recording a programme until X hours after it was added to get_iplayer's data cache.