I am really, really struggling to understand why the author bought the Play 3s to start with. The sound quality of Sonos really isn't _that_ great, for the money. It makes a ton of sense only if you want whole-house audio, with speakers in every room, that is fairly unobtrusive. (to put the SQ issue in perspective, I just bought a 6 year old pair of Epos M12s from a man who replaced them with Sonos - and as he said, it was a huge step down in quality).
So if you can afford to buy a ton of Sonos and put it in every room - and you are not technical enough to use AirPlay to build something similar yourself - then it is OK. But ONLY if you can afford enough Sonos speakers to really make it worth it! So if you are in an income bracket where you can do that, the Playbar shouldn't even be a second thought - it works, it fits your system approach, take it to the checkout.
But as the author states, he can't afford it. So what good are the Play 3s? They are a whole-house audio solution that is lacking the funding for expansion to the whole-house.
For £400 to 500 or so, the author could have gotten a pretty nice AV receiver, and a decent sat/sub package in a bundle deal from any high street audio store (Richer Sounds or similar). That would have included a centre channel speaker. And full multi-channel decoding, and video switching capability.
IMHO, sell the Play 3s to someone that needs whole-house audio, and go buy a good system for your AV needs...