WMP can play files from a DLNA server. You need to have network discovery switched on, then DLNA servers become visible under network (explorer). In Windows 10, there is a new video player 'Films and TV' but I have not done much with it.
Downloaded and installed K-Lite Codec Pack and all OK now
Finally cracked this one and can now play both SD and HD files in WMP streamed or downloaded on the network from the Humax. This is how I did it:-
Apparently its a codec problem so first thing to do is to download the mega pack for K Lite from codecguide Install it and then download Win7DSFilterTweaker from the same website The DSfilter tweaker will run from the downloaded exe file so you wont need to install it as such, just click on it to load. Once loaded click on the middle of the three buttons marked "tweeks" this brings up a dialogue and you need to tick the first box "Microsoft DTV-DVD Audio Decoder" and the last box "Media Foundation" to disable these codecs in WMP. Save and exit out of the program. Now click on the downloaded or streamed Humax files in SD and they should load up and play correctly in WMP.
ps sorry about not giving actual links but apparently I haven't posted enough yet to avoid the spam detector If someone could post the links for me I'd be grateful.