@Sunshine, thanks fro responding. 

yes, I am using different bits of kit in the network. It is only the older 4220 from which I can get any WiFi at all, it gives me 8 Meg, which I think is labelled 294D on this diagram. So I know the 8010 unit connected to the router is sending out some connectivity. 

I reset the unit labelled C3B5 here, as previously I had connected it using WPS, so it was harder to distinguish what the problem was. 

I now can get connectivity using Eternet, between 75 and 15 Mg depending on what room I am in. But I can't connect via Wifi at all, it is not throwing out a signal.

It feels like part of the problem is the 8010 unit. the middle light flikers between green / orange / red, but sometimes there is no light at all. 

Hi  @Sunshine, the 8010 unit is connected to the router, it is the C5C2 unit in this diagram. The topology on the screenshot doesn't look right to me, but that is what it shows.  

The point I was making on my last post, is that i reset C3B5 so it is distinguishable, and whilst it works if i connect with an Ethernet cable, the WiFi doesn't' work wven though the WiFi lights are green. The only light that is not on is the middle one, but this lights up green when I connect via a cable. 

  @SJGW Hi, any further thoughts on this?

 Hi sunshine, unfortunately the whole system no longer appears to be working. 

the middle light on the 8010 unit is totally dark, it never had any colour. 

How can I sort this?

  @SJGW According to the lights on the extenders, they are paired. 

but no internet is being transmitted from the 8010 unit.