This is starting to drive me nuts now!
Twonky is serving me fairly well, but still has issues with the selected player (ie Denon hifi) disappearing at random, although the music will often continue when this happens. Sometimes it's still there, but player window reverts to "TwonkyPlayer". Also the NAS drive sometimes vanishes from the list. At other times, the music will play for 5 or 6 tracks with no issue, but at others, a fresh start is required for each song!
Back to iTunes. More research revealed that older versions (10 as opposed to 11) were better at streaming, so "down-graded" to 10, only to hit the same issues, which were dropouts every minute or so, and lock-ups every 5 minutes or so
OK, try something else then.... What about WinAmp? I'd used this years ago and forgotten about it. Turns out it's future is in jeopardy, with imminent axing, but managed to download a copy. Onto this I installed a plugin called "Remote Speakers". For a wonderful five minutes, I thought this was my solution, but then it started all over again! Annoyingly, "Remote Speakers" uses AirPlay and it seems the latter is the cause of the problems. Basically any player on the laptop will play without issue using the built-in speakers, the hifi will stream without issue using it's own interface to select music, and Twonky plays with no stops within tracks (although it may fail to buffer the next one). Bring AirPlay into the equation and the problems begin.
If I was on Windows 7 I could have the latest Media Player and stream from that, avoiding any other programs or servers, but annoyingly, this looks to be something I can't have until I get a new laptop
(OK, even that's not guaranteed to work, but how annoying is this whole thing!)