Tvheadend

I have a TBSDTV MOI box which is a self contained linux tuner server running tvheadend. I have everything working fine except for the record destination. I would like to record to a NFS share on a NAS box (running FreeNAS). I have the NFS share set up and checked by looking at it on a separate linux computer. The share folder is mnt/MitchNAS/XBMC/TV_Recordings
I have thus entered as the path in the tvheadend browser panel:
nfs://192.168.1.67:/mnt/MitchNAS/XBMC/TV_Recordings

rather bizarrely (at least to my mind) if I start a recording then it is actually recording to somewhere on the Windows computer that is running the browser interface to tvheadend. Can somebody at least check that I have the protocol correct for the NAS address?
thanks