So, small update as I'm slightly puzzled by what's happening.
Moved router closer to all devices. Speed test says 150% better speed than in the same spot pre-move, great. But the Sonos system now seems to be much more disrupted (e.g. when I ran the speed test, sonos completely stopped until it was finished).
Current devices are:
Macbook, iphone, 2x Sonos Play 1 connected wirelessly to single router.
LG smart tv wired connection to same router (tv turned off most of the time).
I know Sonos have a bit of a reputation for network disruption, but anything obvious I'm missing? Thanks