Basic switch....should I upgrade?

Since you have an etherregen: get an ocxo clock (AfterDark, Mutec, Cybershaft or other) You can start with a $100 Chinese clock on aliexpress and the upgrade if worthwhile. I also found dxe filters on the ethernet beneficial. Make sure the Etherregen has a strong ground connection from its post.

Bought a cheap switch Cisco SG110D-08 on EBay UK.

Getting a clock installed for this by fidelityaudio.co.uk

Sent to me (not in the UK).

Way cheaper than any other option I could see for an audiophile switch.

Also bought a Cisco 2960 and was upgraded by audiophool.nl

The Cisco 2960 is a fantastic bargain second hand. It is a brilliantly made switch, made in the millions. Despite huge production runs the switch is expensive  new as it is so well made. Compare that to audio switches which are made in the thousands and you can see that the quality of a Cisco is up there with the best audio switches.  I have tested a few switches and the Cisco at $50 on eBay is as good as any.
The other great thing about the Cisco is that it has an optical input/output. You may find you get a better result if you run optical from this switch to the etherregen and then take ethernet from the cleaned and isolated single ethernet ‘out’ to the streamer/bridge.  This is how the etherregen is intended to be used as the single output from its ‘B’ side gives unparalleled clean ethernet to the streamer.  Or, if you are running optical into your streamer/bridge you will probably find that an optical out from the Cisco switch straight into the streamer, therefore bypassing the etherregen, will be just as good since optical fibre is the cleanest of cleanest connections  

@ghdprentice depends on how bad the switch is. D Link are among the worst consumer equipment out there, so there is a real possibility that the streamer chache and tcp/ip can’t cover for it.

What is clear is that you can’t plug use a bad switch, and then add another device to clean up the bad switch output. That’s not how things work in networking. 
 

Also, Audio Science Review have some thoughts on this topic too.