Do you also have a delay when playing from apps on your TV or cable/terrestrial?

I see are using two extractors? You could try try if the problem goes away when you connect the Beam directly to HDMI-ARC in the TV using the Sonos supplied HDMI cable and the Google streamer to another HDMI.

Sorry I am not using the Sonos optical cable, but  i do not have the issue when using Firestick or terrestrial TV.

I have decided to return the Google TV streamer and the hdmi extractor and look for a comparable box that will not cause all the issues I'm getting 

I’d agree, any transfer to optical, one way or another, is going to take time. I’d definitely be connecting the Beam to the TV via the Sonos supplied HDMI cable to the TV’s ARC (or eARC) port (which is HDMI 2, based on this webpage). Not sure I understand why, in the OP, there are two devices that transfer sound to optical, when this TV is equipped with ARC. 

If there’s still any delay, I’d be checking both the TV and the streaming device for updates. I’ve not seen that any updates for Sonos introduced delay, but it certainly wouldn’t hurt checking that for updates as well. 
 

I also have to ask why you are using the extractors?  The LG OLED55C8PLA TV has an HDMI-ARC port, just connect the Beam to that using HDMI.  HDMI-ARC is going to give you better quality from streaming sources (DD+ instead of plain DD) and you don’t need to fool with so many boxes and extra optical cables. 

I was actually trying a different box as am concerned about amazon policy and their changing thier operating system to vega to stop sideloading apps

But that shouldn’t have any effect on what connection you have from the TV to the Beam.  It’s still not clear why you are using optical to the Beam when you have a fully HDMI-ARC capable TV and soundbar.

Because the advice I was given was that the optical would work around the fact that my tv only has hdmi arc and not earc, but its all irrelevant as i am now using a firestick that has solved the problem that all the expensive modern boxes could not. old technology is not compatible with new and new is not backward compatible. Mind you all this goes above my head I just follow guidance lol

The advice you were given isn’t correct. Optical is less capable than ARC which is less capable then eARC. You should use hdmi from the TV HDMI/ARC port to the Beam.

I am now but using the Google streamer I am having all sorts of lip sync issues and picture quality issues so have switched back to my old Firestick 4k and magic all the issues have disappeared. My cheap Firestick works better than my Formuler z10 pro and a brand new Google TV streamer 4k both costing over 130 euros and the Firestick 40 euros 

Sonos HDMI-ARC soundbars are fully capable of using an HDMI-ARC connection instead of eARC.  Matter of fact, the only advantage for eARC is it allows Dolby TrueHD lossless, which streaming services don’t use, only Blu-Ray.

Yes it was that I wanted to buy a better quality box than the firestick but it seems the Firestick is better than all the expensive ones anyway with my system as it's the only one without lip sync issues 

Many different Firesticks and picking a good one matters. We have 4K Max ones in our primary TV sets. Resolution is important if you have a 4K set but the 4K works fine on our old HD Sony too. CPU and memory matter, even if you don't do anything fancy, the faster response to commands is worth the few dollars more. Not saying the others are bad, we have a couple so old they have been discontinued still working in other rooms.

I've seen articles about newer devices, sound interesting. Not getting the "horrors" over sideloading being gone on newer models. We haven't done since we got started many years ago so it isn't an issue here.

On the new versions, we will wait for user reports, not so much professional reviewers, and may upgrade if there are significant upgrades available. Like with our Sonos the replaced units will move to other locations displacing the oldest ones.

There is a lot more to the Vega story than stopping sideloading. Worth reading about if you are concerned.

https://www.bsgroup.eu/blog/what-is-amazon-vega-os-and-why-it-matters-for-fire-tv-users/

And I see the reason some folks are unhappy.

https://www.tomsguide.com/entertainment/streaming-devices/amazons-new-usd40-fire-stick-is-the-illegal-streamers-nightmare-heres-why

Hence why I wanted to move away from Amazon