Right.... I apologise for the millions of posts, but as has been expertly illustrated by lucid, this is a much deeper subject than it appears!
I've got to say, I love this forum, i really appreciate both the depth of knowledge and willingness to help of it's members.
I've decided on the straight up Sonos, full 5.1 setup. It's wireless, it's aesthetic, the physical setup (no front side speakers) suits my room best, and I'm no audiophile so it'll be a huge step up from just using the tv speakers. The music streamed will be from Apple Music so it won't be HD audio.
Most importantly, as far as I can tell, I will get 5.1 audio.
Unless of course any of what I've got below is wrong??
My TV outputs Dolby Digital:-
http://m.johnlewis.com/mt/www.johnl...ew-hd-and-built-in-wi-fi/p1919512#page_loaded
The Playbar will output 5.1 sound from a Dolby digital signal (I don't even know if signal is the right word!), and the PS4 will decode DTS to DD itself...
https://en.community.sonos.com/home-theater-228993/dts-dolby-51-on-playbar-2015-edition-6731191
The only 5.1 I need is from the PS4. I use it for Blu Ray and Netflix. I don't care about 5.1 coming from the sky box.
Plus, if this fails, as lucid points out in the very first reply here, I can always get an optical switch....
I will update this as soon as it's all bought, but I'll be checking back in case anyone's spotted any glaring errors?