I ended up buying an x-box 360 from a mate at work for £100! the deal included a £20 remote and £50 802.11 wireless network adaptor! (I know it was all his kit and NOT hot
so deal of the century I think
The kids (all over 20 but still kids to me
) have taken it over as a games machine a lot of the time but it streams my photos (including 46mb tiffs!) and MP3 / WMA files fine. It will also handle video I think but I'm not into that at the moment.
The only requirement is to run Windows Media Connect server software(free) on one of the PCs on the network in order that the x-box knows where the files are (and the data folders can be mapped drives on another machine on the network or external USB drives if required). Obviously the machine running WMC needs to be powered up but you don't need to be logged on.
The x-box interface is fairly basic but you can navigate through folders and it will run basic slide-shows. It does what it says on the tin though and I (and more importantly 'er indoors) now get to look at my pictures full-screen on our 37" widescreen TV using an HD connection.
So, problem solved - until I find something better