Update: Thanks to suffering egg in my face elsewhere, I can now confirm that XBMC can stream (albeit stuttery on my system) full HiDef as well as StDef from the HDR-FOX native DLNA server, as long as auto-unprotect has been used to clear all the content protection (not just Foxy, or - I believe - WebIF OPT+). It needs further investigation, but I can't see HiDef recordings in the My Video directory, only subdirectories.
The stutteriness may be a configuration problem on my part, but as I have no immediate requirement for this means of playback I do not intend to work it out.
Even if playback was smooth, I can't give it five stars because there is absolutely no transport control - play, pause, stop - that's all. Although this "solves" the hunt for a DLNA client, I think mounting the HDR-FOX's drive as a network share and then using Splash Player Lite to play the file as if it were local is a better bet, which is a practical proposition now we have decrypt-in-place available to remove all the remaining rights management.
The best DLNA client is still an HD-FOX.