Thanks beefypigeon - I need to get my head round AirPlay (and AppleTV). I think both would have many benefits for my (Mac-centric) set up.
http://www.bowers-wilkins.co.uk/Wireless-Speakers/Wireless-Speakers/Wireless-Speakers/airplay.html
A word of caution re SONOS. I bought a Play:1 speaker recently with a view to getting some more.
First thing that was not obvious to me was the requirement to download and use the SONOS desktop app.
No probs I reasoned, so I downloaded it for Mac and used it to add my iTunes library, but after...